diff --git a/package-lock.json b/package-lock.json
index 82cb37f8..552b4ee6 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -44,6 +44,7 @@
         "csv-stringify": "^6.7.0",
         "cypress": "^15.14.2",
         "del": "^8.0.1",
+        "exceljs": "^4.4.0",
         "firebase": "^12.13.0",
         "gulp": "^5.0.1",
         "gulp-env": "^0.4.0",
@@ -55,6 +56,7 @@
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         "jest": "^30.4.2",
         "jest-environment-jsdom": "^30.4.1",
+        "jszip": "^3.10.1",
         "moment": "^2.30.1",
         "moment-timezone": "^0.6.2",
         "pdfmake": "^0.3.8",
@@ -2379,6 +2381,51 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/@fast-csv/format": {
+      "version": "4.3.5",
+      "resolved": "https://registry.npmjs.org/@fast-csv/format/-/format-4.3.5.tgz",
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+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
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+        "lodash.escaperegexp": "^4.1.2",
+        "lodash.isboolean": "^3.0.3",
+        "lodash.isequal": "^4.5.0",
+        "lodash.isfunction": "^3.0.9",
+        "lodash.isnil": "^4.0.0"
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+    "node_modules/@fast-csv/format/node_modules/@types/node": {
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+      "resolved": "https://registry.npmjs.org/@types/node/-/node-14.18.63.tgz",
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+      "dev": true,
+      "license": "MIT"
+    },
+    "node_modules/@fast-csv/parse": {
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+      "resolved": "https://registry.npmjs.org/@fast-csv/parse/-/parse-4.3.6.tgz",
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+      "dev": true,
+      "license": "MIT",
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+        "lodash.escaperegexp": "^4.1.2",
+        "lodash.groupby": "^4.6.0",
+        "lodash.isfunction": "^3.0.9",
+        "lodash.isnil": "^4.0.0",
+        "lodash.isundefined": "^3.0.1",
+        "lodash.uniq": "^4.5.0"
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+    "node_modules/@fast-csv/parse/node_modules/@types/node": {
+      "version": "14.18.63",
+      "resolved": "https://registry.npmjs.org/@types/node/-/node-14.18.63.tgz",
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+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/@firebase/ai": {
       "version": "2.13.1",
       "resolved": "https://registry.npmjs.org/@firebase/ai/-/ai-2.13.1.tgz",
@@ -5236,9 +5283,6 @@
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@@ -5253,9 +5297,6 @@
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@@ -5270,9 +5311,6 @@
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@@ -5287,9 +5325,6 @@
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@@ -5304,9 +5339,6 @@
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@@ -5321,9 +5353,6 @@
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@@ -5338,9 +5367,6 @@
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@@ -5355,9 +5381,6 @@
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@@ -5372,9 +5395,6 @@
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@@ -5389,9 +5409,6 @@
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@@ -5406,9 +5423,6 @@
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@@ -5423,9 +5437,6 @@
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@@ -5440,9 +5451,6 @@
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@@ -6437,9 +6445,6 @@
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@@ -6454,9 +6459,6 @@
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@@ -6471,9 +6473,6 @@
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@@ -6488,9 +6487,6 @@
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@@ -6505,9 +6501,6 @@
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@@ -6522,9 +6515,6 @@
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@@ -6539,9 +6529,6 @@
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-        "musl"
-      ],
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@@ -6556,9 +6543,6 @@
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@@ -6573,9 +6557,6 @@
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-      ],
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@@ -6590,9 +6571,6 @@
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-        "musl"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -7096,6 +7074,112 @@
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       "license": "MIT"
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+      "resolved": "https://registry.npmjs.org/archiver/-/archiver-5.3.2.tgz",
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+      "license": "MIT",
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+        "async": "^3.2.4",
+        "buffer-crc32": "^0.2.1",
+        "readable-stream": "^3.6.0",
+        "readdir-glob": "^1.1.2",
+        "tar-stream": "^2.2.0",
+        "zip-stream": "^4.1.0"
+      },
+      "engines": {
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+        "graceful-fs": "^4.2.0",
+        "lazystream": "^1.0.0",
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+      "resolved": "https://registry.npmjs.org/safe-buffer/-/safe-buffer-5.1.2.tgz",
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+      "resolved": "https://registry.npmjs.org/readable-stream/-/readable-stream-3.6.2.tgz",
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+      "license": "MIT",
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+        "inherits": "^2.0.3",
+        "string_decoder": "^1.1.1",
+        "util-deprecate": "^1.0.1"
+      },
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+      "resolved": "https://registry.npmjs.org/string_decoder/-/string_decoder-1.3.0.tgz",
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@@ -7733,6 +7817,30 @@
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+      "version": "1.6.52",
+      "resolved": "https://registry.npmjs.org/big-integer/-/big-integer-1.6.52.tgz",
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+      "dev": true,
+      "license": "Unlicense",
+      "engines": {
+        "node": ">=0.6"
+      }
+    },
+    "node_modules/binary": {
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+      "resolved": "https://registry.npmjs.org/binary/-/binary-0.3.0.tgz",
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+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "buffers": "~0.1.1",
+        "chainsaw": "~0.1.0"
+      },
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@@ -8015,6 +8123,16 @@
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+      "version": "0.2.13",
+      "resolved": "https://registry.npmjs.org/buffer-crc32/-/buffer-crc32-0.2.13.tgz",
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+      "dev": true,
+      "license": "MIT",
+      "engines": {
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@@ -8022,6 +8140,25 @@
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+      "resolved": "https://registry.npmjs.org/buffer-indexof-polyfill/-/buffer-indexof-polyfill-1.0.2.tgz",
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+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=0.10"
+      }
+    },
+    "node_modules/buffers": {
+      "version": "0.1.1",
+      "resolved": "https://registry.npmjs.org/buffers/-/buffers-0.1.1.tgz",
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+      "dev": true,
+      "engines": {
+        "node": ">=0.2.0"
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@@ -8194,6 +8331,19 @@
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+      "resolved": "https://registry.npmjs.org/chainsaw/-/chainsaw-0.1.0.tgz",
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+      "license": "MIT/X11",
+      "dependencies": {
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@@ -8620,6 +8770,47 @@
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+      "license": "MIT",
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+        "crc32-stream": "^4.0.2",
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+        "readable-stream": "^3.6.0"
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+      "engines": {
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+      "resolved": "https://registry.npmjs.org/readable-stream/-/readable-stream-3.6.2.tgz",
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+      "license": "MIT",
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+        "string_decoder": "^1.1.1",
+        "util-deprecate": "^1.0.1"
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+      "resolved": "https://registry.npmjs.org/string_decoder/-/string_decoder-1.3.0.tgz",
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+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
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@@ -8781,6 +8972,58 @@
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+      "version": "1.2.2",
+      "resolved": "https://registry.npmjs.org/crc-32/-/crc-32-1.2.2.tgz",
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+      "dev": true,
+      "license": "Apache-2.0",
+      "bin": {
+        "crc32": "bin/crc32.njs"
+      },
+      "engines": {
+        "node": ">=0.8"
+      }
+    },
+    "node_modules/crc32-stream": {
+      "version": "4.0.3",
+      "resolved": "https://registry.npmjs.org/crc32-stream/-/crc32-stream-4.0.3.tgz",
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+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "crc-32": "^1.2.0",
+        "readable-stream": "^3.4.0"
+      },
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+    },
+    "node_modules/lodash.isnil": {
+      "version": "4.0.0",
+      "resolved": "https://registry.npmjs.org/lodash.isnil/-/lodash.isnil-4.0.0.tgz",
+      "integrity": "sha512-up2Mzq3545mwVnMhTDMdfoG1OurpA/s5t88JmQX809eH3C8491iu2sfKhTfhQtKY78oPNhiaHJUpT/dUDAAtng==",
+      "dev": true,
+      "license": "MIT"
+    },
+    "node_modules/lodash.isplainobject": {
+      "version": "4.0.6",
+      "resolved": "https://registry.npmjs.org/lodash.isplainobject/-/lodash.isplainobject-4.0.6.tgz",
+      "integrity": "sha512-oSXzaWypCMHkPC3NvBEaPHf0KsA5mvPrOPgQWDsbg8n7orZ290M0BmC/jgRZ4vcJ6DTAhjrsSYgdsW/F+MFOBA==",
+      "dev": true,
+      "license": "MIT"
+    },
+    "node_modules/lodash.isundefined": {
+      "version": "3.0.1",
+      "resolved": "https://registry.npmjs.org/lodash.isundefined/-/lodash.isundefined-3.0.1.tgz",
+      "integrity": "sha512-MXB1is3s899/cD8jheYYE2V9qTHwKvt+npCwpD+1Sxm3Q3cECXCiYHjeHWXNwr6Q0SOBPrYUDxendrO6goVTEA==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/lodash.keys": {
       "version": "3.1.2",
       "resolved": "https://registry.npmjs.org/lodash.keys/-/lodash.keys-3.1.2.tgz",
@@ -14901,6 +15449,20 @@
         "lodash.escape": "^3.0.0"
       }
     },
+    "node_modules/lodash.union": {
+      "version": "4.6.0",
+      "resolved": "https://registry.npmjs.org/lodash.union/-/lodash.union-4.6.0.tgz",
+      "integrity": "sha512-c4pB2CdGrGdjMKYLA+XiRDO7Y0PRQbm/Gzg8qMj+QH+pFVAoTp5sBpO0odL3FjoPCGjK96p6qsP+yQoiLoOBcw==",
+      "dev": true,
+      "license": "MIT"
+    },
+    "node_modules/lodash.uniq": {
+      "version": "4.5.0",
+      "resolved": "https://registry.npmjs.org/lodash.uniq/-/lodash.uniq-4.5.0.tgz",
+      "integrity": "sha512-xfBaXQd9ryd9dlSDvnvI0lvxfLJlYAZzXomUYzLKtUeOQvOP5piqAWuGtrhWeqaXK9hhoM/iyJc5AV+XfsX3HQ==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/log-symbols": {
       "version": "4.1.0",
       "resolved": "https://registry.npmjs.org/log-symbols/-/log-symbols-4.1.0.tgz",
@@ -15376,6 +15938,19 @@
         "node": ">=16 || 14 >=14.17"
       }
     },
+    "node_modules/mkdirp": {
+      "version": "0.5.6",
+      "resolved": "https://registry.npmjs.org/mkdirp/-/mkdirp-0.5.6.tgz",
+      "integrity": "sha512-FP+p8RB8OWpF3YZBCrP5gtADmtXApB5AMLn+vdyA+PyxCjrCs00mjyUozssO33cwDeT3wNGdLxJ5M//YqtHAJw==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "minimist": "^1.2.6"
+      },
+      "bin": {
+        "mkdirp": "bin/cmd.js"
+      }
+    },
     "node_modules/moment": {
       "version": "2.30.1",
       "resolved": "https://registry.npmjs.org/moment/-/moment-2.30.1.tgz",
@@ -16997,6 +17572,39 @@
         "string_decoder": "~0.10.x"
       }
     },
+    "node_modules/readdir-glob": {
+      "version": "1.1.3",
+      "resolved": "https://registry.npmjs.org/readdir-glob/-/readdir-glob-1.1.3.tgz",
+      "integrity": "sha512-v05I2k7xN8zXvPD9N+z/uhXPaj0sUFCe2rcWZIpBsqxfP7xXFQ0tipAd/wjj1YxWyWtUS5IDJpOG82JKt2EAVA==",
+      "dev": true,
+      "license": "Apache-2.0",
+      "dependencies": {
+        "minimatch": "^5.1.0"
+      }
+    },
+    "node_modules/readdir-glob/node_modules/brace-expansion": {
+      "version": "2.1.4",
+      "resolved": "https://registry.npmjs.org/brace-expansion/-/brace-expansion-2.1.4.tgz",
+      "integrity": "sha512-hGfVzPxthbf3+2yjg/RBs60cB0FhqBS/zvdV/4wn4/BmN0bNMMHPc4V/BbFieqf1TKAGGAHnY4eSjajCl0f2Xg==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "balanced-match": "^1.0.0"
+      }
+    },
+    "node_modules/readdir-glob/node_modules/minimatch": {
+      "version": "5.1.9",
+      "resolved": "https://registry.npmjs.org/minimatch/-/minimatch-5.1.9.tgz",
+      "integrity": "sha512-7o1wEA2RyMP7Iu7GNba9vc0RWWGACJOCZBJX2GJWip0ikV+wcOsgVuY9uE8CPiyQhkGFSlhuSkZPavN7u1c2Fw==",
+      "dev": true,
+      "license": "ISC",
+      "dependencies": {
+        "brace-expansion": "^2.0.1"
+      },
+      "engines": {
+        "node": ">=10"
+      }
+    },
     "node_modules/readdirp": {
       "version": "3.6.0",
       "resolved": "https://registry.npmjs.org/readdirp/-/readdirp-3.6.0.tgz",
@@ -17424,6 +18032,20 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/rimraf": {
+      "version": "2.7.1",
+      "resolved": "https://registry.npmjs.org/rimraf/-/rimraf-2.7.1.tgz",
+      "integrity": "sha512-uWjbaKIK3T1OSVptzX7Nl6PvQ3qAGtKEtVRjRuazjfL3Bx5eI409VZSqgND+4UNnmzLVdPj9FqFJNPqBZFve4w==",
+      "deprecated": "Rimraf versions prior to v4 are no longer supported",
+      "dev": true,
+      "license": "ISC",
+      "dependencies": {
+        "glob": "^7.1.3"
+      },
+      "bin": {
+        "rimraf": "bin.js"
+      }
+    },
     "node_modules/rollup": {
       "version": "4.62.2",
       "resolved": "https://registry.npmjs.org/rollup/-/rollup-4.62.2.tgz",
@@ -17929,6 +18551,13 @@
         "node": ">= 0.4"
       }
     },
+    "node_modules/setimmediate": {
+      "version": "1.0.5",
+      "resolved": "https://registry.npmjs.org/setimmediate/-/setimmediate-1.0.5.tgz",
+      "integrity": "sha512-MATJdZp8sLqDl/68LfQmbP8zKPLQNV6BIZoIgrscFDQ+RsvK/BxeDQOgyxKKoh0y/8h3BqVFnCqQ/gd+reiIXA==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/setprototypeof": {
       "version": "1.2.0",
       "resolved": "https://registry.npmjs.org/setprototypeof/-/setprototypeof-1.2.0.tgz",
@@ -18915,6 +19544,60 @@
         "url": "https://opencollective.com/webpack"
       }
     },
+    "node_modules/tar-stream": {
+      "version": "2.2.0",
+      "resolved": "https://registry.npmjs.org/tar-stream/-/tar-stream-2.2.0.tgz",
+      "integrity": "sha512-ujeqbceABgwMZxEJnk2HDY2DlnUZ+9oEcb1KzTVfYHio0UE6dG71n60d8D2I4qNvleWrrXpmjpt7vZeF1LnMZQ==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "bl": "^4.0.3",
+        "end-of-stream": "^1.4.1",
+        "fs-constants": "^1.0.0",
+        "inherits": "^2.0.3",
+        "readable-stream": "^3.1.1"
+      },
+      "engines": {
+        "node": ">=6"
+      }
+    },
+    "node_modules/tar-stream/node_modules/bl": {
+      "version": "4.1.0",
+      "resolved": "https://registry.npmjs.org/bl/-/bl-4.1.0.tgz",
+      "integrity": "sha512-1W07cM9gS6DcLperZfFSj+bWLtaPGSOHWhPiGzXmvVJbRLdG82sH/Kn8EtW1VqWVA54AKf2h5k5BbnIbwF3h6w==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "buffer": "^5.5.0",
+        "inherits": "^2.0.4",
+        "readable-stream": "^3.4.0"
+      }
+    },
+    "node_modules/tar-stream/node_modules/readable-stream": {
+      "version": "3.6.2",
+      "resolved": "https://registry.npmjs.org/readable-stream/-/readable-stream-3.6.2.tgz",
+      "integrity": "sha512-9u/sniCrY3D5WdsERHzHE4G2YCXqoG5FTHUiCC4SIbr6XcLZBY05ya9EKjYek9O5xOAwjGq+1JdGBAS7Q9ScoA==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "inherits": "^2.0.3",
+        "string_decoder": "^1.1.1",
+        "util-deprecate": "^1.0.1"
+      },
+      "engines": {
+        "node": ">= 6"
+      }
+    },
+    "node_modules/tar-stream/node_modules/string_decoder": {
+      "version": "1.3.0",
+      "resolved": "https://registry.npmjs.org/string_decoder/-/string_decoder-1.3.0.tgz",
+      "integrity": "sha512-hkRX8U1WjJFd8LsDJ2yQ/wWWxaopEsABU1XfkM8A+j0+85JAGppt16cr1Whg6KIbb4okU6Mql6BOj+uup/wKeA==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "safe-buffer": "~5.2.0"
+      }
+    },
     "node_modules/teex": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/teex/-/teex-1.0.1.tgz",
@@ -19329,6 +20012,16 @@
         "node": ">=18"
       }
     },
+    "node_modules/traverse": {
+      "version": "0.3.9",
+      "resolved": "https://registry.npmjs.org/traverse/-/traverse-0.3.9.tgz",
+      "integrity": "sha512-iawgk0hLP3SxGKDfnDJf8wTz4p2qImnyihM5Hh/sGvQ3K37dPi/w8sRhdNIxYA1TwFwc5mDhIJq+O0RsvXBKdQ==",
+      "dev": true,
+      "license": "MIT/X11",
+      "engines": {
+        "node": "*"
+      }
+    },
     "node_modules/tree-dump": {
       "version": "1.1.0",
       "resolved": "https://registry.npmjs.org/tree-dump/-/tree-dump-1.1.0.tgz",
@@ -19751,6 +20444,82 @@
         "node": ">=8"
       }
     },
+    "node_modules/unzipper": {
+      "version": "0.10.14",
+      "resolved": "https://registry.npmjs.org/unzipper/-/unzipper-0.10.14.tgz",
+      "integrity": "sha512-ti4wZj+0bQTiX2KmKWuwj7lhV+2n//uXEotUmGuQqrbVZSEGFMbI68+c6JCQ8aAmUWYvtHEz2A8K6wXvueR/6g==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "big-integer": "^1.6.17",
+        "binary": "~0.3.0",
+        "bluebird": "~3.4.1",
+        "buffer-indexof-polyfill": "~1.0.0",
+        "duplexer2": "~0.1.4",
+        "fstream": "^1.0.12",
+        "graceful-fs": "^4.2.2",
+        "listenercount": "~1.0.1",
+        "readable-stream": "~2.3.6",
+        "setimmediate": "~1.0.4"
+      }
+    },
+    "node_modules/unzipper/node_modules/bluebird": {
+      "version": "3.4.7",
+      "resolved": "https://registry.npmjs.org/bluebird/-/bluebird-3.4.7.tgz",
+      "integrity": "sha512-iD3898SR7sWVRHbiQv+sHUtHnMvC1o3nW5rAcqnq3uOn07DSAppZYUkIGslDz6gXC7HfunPe7YVBgoEJASPcHA==",
+      "dev": true,
+      "license": "MIT"
+    },
+    "node_modules/unzipper/node_modules/duplexer2": {
+      "version": "0.1.4",
+      "resolved": "https://registry.npmjs.org/duplexer2/-/duplexer2-0.1.4.tgz",
+      "integrity": "sha512-asLFVfWWtJ90ZyOUHMqk7/S2w2guQKxUI2itj3d92ADHhxUSbCMGi1f1cBcJ7xM1To+pE/Khbwo1yuNbMEPKeA==",
+      "dev": true,
+      "license": "BSD-3-Clause",
+      "dependencies": {
+        "readable-stream": "^2.0.2"
+      }
+    },
+    "node_modules/unzipper/node_modules/isarray": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/isarray/-/isarray-1.0.0.tgz",
+      "integrity": "sha512-VLghIWNM6ELQzo7zwmcg0NmTVyWKYjvIeM83yjp0wRDTmUnrM678fQbcKBo6n2CJEF0szoG//ytg+TKla89ALQ==",
+      "dev": true,
+      "license": "MIT"
+    },
+    "node_modules/unzipper/node_modules/readable-stream": {
+      "version": "2.3.8",
+      "resolved": "https://registry.npmjs.org/readable-stream/-/readable-stream-2.3.8.tgz",
+      "integrity": "sha512-8p0AUk4XODgIewSi0l8Epjs+EVnWiK7NoDIEGU0HhE7+ZyY8D1IMY7odu5lRrFXGg71L15KG8QrPmum45RTtdA==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "core-util-is": "~1.0.0",
+        "inherits": "~2.0.3",
+        "isarray": "~1.0.0",
+        "process-nextick-args": "~2.0.0",
+        "safe-buffer": "~5.1.1",
+        "string_decoder": "~1.1.1",
+        "util-deprecate": "~1.0.1"
+      }
+    },
+    "node_modules/unzipper/node_modules/safe-buffer": {
+      "version": "5.1.2",
+      "resolved": "https://registry.npmjs.org/safe-buffer/-/safe-buffer-5.1.2.tgz",
+      "integrity": "sha512-Gd2UZBJDkXlY7GbJxfsE8/nvKkUEU1G38c1siN6QP6a9PT9MmHB8GnpscSmMJSoF8LOIrt8ud/wPtojys4G6+g==",
+      "dev": true,
+      "license": "MIT"
+    },
+    "node_modules/unzipper/node_modules/string_decoder": {
+      "version": "1.1.1",
+      "resolved": "https://registry.npmjs.org/string_decoder/-/string_decoder-1.1.1.tgz",
+      "integrity": "sha512-n/ShnvDi6FHbbVfviro+WojiFzv+s8MPMHBczVePfUpDJLwoLT0ht1l4YwBCbi8pJAveEEdnkHyPyTP/mzRfwg==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "safe-buffer": "~5.1.0"
+      }
+    },
     "node_modules/upath": {
       "version": "1.2.0",
       "resolved": "https://registry.npmjs.org/upath/-/upath-1.2.0.tgz",
@@ -21343,6 +22112,68 @@
       "funding": {
         "url": "https://github.com/sponsors/sindresorhus"
       }
+    },
+    "node_modules/zip-stream": {
+      "version": "4.1.1",
+      "resolved": "https://registry.npmjs.org/zip-stream/-/zip-stream-4.1.1.tgz",
+      "integrity": "sha512-9qv4rlDiopXg4E69k+vMHjNN63YFMe9sZMrdlvKnCjlCRWeCBswPPMPUfx+ipsAWq1LXHe70RcbaHdJJpS6hyQ==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "archiver-utils": "^3.0.4",
+        "compress-commons": "^4.1.2",
+        "readable-stream": "^3.6.0"
+      },
+      "engines": {
+        "node": ">= 10"
+      }
+    },
+    "node_modules/zip-stream/node_modules/archiver-utils": {
+      "version": "3.0.4",
+      "resolved": "https://registry.npmjs.org/archiver-utils/-/archiver-utils-3.0.4.tgz",
+      "integrity": "sha512-KVgf4XQVrTjhyWmx6cte4RxonPLR9onExufI1jhvw/MQ4BB6IsZD5gT8Lq+u/+pRkWna/6JoHpiQioaqFP5Rzw==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "glob": "^7.2.3",
+        "graceful-fs": "^4.2.0",
+        "lazystream": "^1.0.0",
+        "lodash.defaults": "^4.2.0",
+        "lodash.difference": "^4.5.0",
+        "lodash.flatten": "^4.4.0",
+        "lodash.isplainobject": "^4.0.6",
+        "lodash.union": "^4.6.0",
+        "normalize-path": "^3.0.0",
+        "readable-stream": "^3.6.0"
+      },
+      "engines": {
+        "node": ">= 10"
+      }
+    },
+    "node_modules/zip-stream/node_modules/readable-stream": {
+      "version": "3.6.2",
+      "resolved": "https://registry.npmjs.org/readable-stream/-/readable-stream-3.6.2.tgz",
+      "integrity": "sha512-9u/sniCrY3D5WdsERHzHE4G2YCXqoG5FTHUiCC4SIbr6XcLZBY05ya9EKjYek9O5xOAwjGq+1JdGBAS7Q9ScoA==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "inherits": "^2.0.3",
+        "string_decoder": "^1.1.1",
+        "util-deprecate": "^1.0.1"
+      },
+      "engines": {
+        "node": ">= 6"
+      }
+    },
+    "node_modules/zip-stream/node_modules/string_decoder": {
+      "version": "1.3.0",
+      "resolved": "https://registry.npmjs.org/string_decoder/-/string_decoder-1.3.0.tgz",
+      "integrity": "sha512-hkRX8U1WjJFd8LsDJ2yQ/wWWxaopEsABU1XfkM8A+j0+85JAGppt16cr1Whg6KIbb4okU6Mql6BOj+uup/wKeA==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "safe-buffer": "~5.2.0"
+      }
     }
   }
 }
diff --git a/package.json b/package.json
index b4374449..083397e8 100644
--- a/package.json
+++ b/package.json
@@ -47,6 +47,7 @@
     "csv-stringify": "^6.7.0",
     "cypress": "^15.14.2",
     "del": "^8.0.1",
+    "exceljs": "^4.4.0",
     "firebase": "^12.13.0",
     "gulp": "^5.0.1",
     "gulp-env": "^0.4.0",
@@ -58,6 +59,7 @@
     "immutability-helper": "^3.1.1",
     "jest": "^30.4.2",
     "jest-environment-jsdom": "^30.4.1",
+    "jszip": "^3.10.1",
     "moment": "^2.30.1",
     "moment-timezone": "^0.6.2",
     "pdfmake": "^0.3.8",
diff --git a/src/components/ReportForm/FormatDropdown.spec.tsx b/src/components/ReportForm/FormatDropdown.spec.tsx
new file mode 100644
index 00000000..524abebf
--- /dev/null
+++ b/src/components/ReportForm/FormatDropdown.spec.tsx
@@ -0,0 +1,45 @@
+import React from 'react';
+import { renderWithTheme, screen, fireEvent } from '../../../test/renderWithTheme';
+import FormatDropdown from './FormatDropdown';
+
+jest.mock('react-i18next', () => ({
+  useTranslation: () => ({ t: key => key }),
+  withTranslation: () => Component => Component,
+}));
+
+jest.mock('scroll-into-view', () => jest.fn());
+
+describe('FormatDropdown', () => {
+  it('renders an input element', () => {
+    renderWithTheme(<FormatDropdown onChange={jest.fn()} />);
+    expect(screen.getByRole('textbox')).toBeInTheDocument();
+  });
+
+  it('offers the pdf and excel options when focused', () => {
+    renderWithTheme(<FormatDropdown onChange={jest.fn()} />);
+    fireEvent.focus(screen.getByRole('textbox'));
+    expect(screen.getByText('invoicesReport.formatPdf')).toBeInTheDocument();
+    expect(screen.getByText('invoicesReport.formatExcel')).toBeInTheDocument();
+  });
+
+  it('calls onChange with the selected format key', () => {
+    const onChange = jest.fn();
+    renderWithTheme(<FormatDropdown onChange={onChange} />);
+    fireEvent.focus(screen.getByRole('textbox'));
+    fireEvent.mouseDown(screen.getByText('invoicesReport.formatExcel'));
+    expect(onChange).toHaveBeenCalledWith('excel');
+  });
+
+  it('renders the current value', () => {
+    renderWithTheme(<FormatDropdown value="excel" onChange={jest.fn()} />);
+    expect(screen.getByRole('textbox')).toHaveValue('invoicesReport.formatExcel');
+  });
+
+  it('does not throw when no onChange is given', () => {
+    renderWithTheme(<FormatDropdown />);
+    fireEvent.focus(screen.getByRole('textbox'));
+    expect(() =>
+      fireEvent.mouseDown(screen.getByText('invoicesReport.formatPdf'))
+    ).not.toThrow();
+  });
+});
diff --git a/src/components/ReportForm/FormatDropdown.tsx b/src/components/ReportForm/FormatDropdown.tsx
new file mode 100644
index 00000000..562bd0aa
--- /dev/null
+++ b/src/components/ReportForm/FormatDropdown.tsx
@@ -0,0 +1,57 @@
+import PropTypes from 'prop-types';
+import React from 'react';
+import styled from 'styled-components';
+import Dropdown from '../Dropdown';
+import { useTranslation } from 'react-i18next';
+
+const Option = styled.div`
+  padding: 0.2em;
+`;
+
+const filterOptions = (options, filter) =>
+  options.filter(option => option.label.toUpperCase().indexOf(filter.toUpperCase()) > -1);
+
+const renderOption = option => <Option>{option.label}</Option>;
+
+const renderValue = option => option.label;
+
+const handleChange = (onChange, value) => {
+  if (typeof onChange === 'function') {
+    onChange(value);
+  }
+};
+
+const FormatDropdown = props => {
+  const { t } = useTranslation();
+  const options = [{
+    key: 'pdf',
+    label: t('invoicesReport.formatPdf')
+  }, {
+    key: 'excel',
+    label: t('invoicesReport.formatExcel')
+  }];
+  return (
+    <Dropdown
+      className={props.className}
+      options={options}
+      value={props.value}
+      onChange={handleChange.bind(null, props.onChange)}
+      readOnly={props.readOnly}
+      optionFilter={filterOptions}
+      optionRenderer={renderOption}
+      valueRenderer={renderValue}
+      optionsRenderLimit={options.length}
+      noOptionsText={t('dropdown.notFound')}
+      mustSelect
+    />
+  );
+};
+
+FormatDropdown.propTypes = {
+  className: PropTypes.string,
+  value: PropTypes.string,
+  onChange: PropTypes.func,
+  readOnly: PropTypes.bool
+};
+
+export default FormatDropdown;
diff --git a/src/components/ReportForm/ReportForm.spec.tsx b/src/components/ReportForm/ReportForm.spec.tsx
index a012708e..0d42e699 100644
--- a/src/components/ReportForm/ReportForm.spec.tsx
+++ b/src/components/ReportForm/ReportForm.spec.tsx
@@ -82,6 +82,22 @@ jest.mock('./DelimiterDropdown', () => {
   };
 });
 
+jest.mock('./FormatDropdown', () => {
+  const React = require('react');
+  return function MockFormatDropdown({ value, onChange }) {
+    return (
+      <select
+        data-testid="format-dropdown"
+        value={value}
+        onChange={e => onChange(e.target.value)}
+      >
+        <option value="pdf">pdf</option>
+        <option value="excel">excel</option>
+      </select>
+    );
+  };
+});
+
 import ReportForm from './ReportForm';
 
 const baseProps = {
@@ -124,6 +140,30 @@ describe('ReportForm', () => {
     expect(screen.getByTestId('delimiter-dropdown')).toBeInTheDocument();
   });
 
+  it('does not render format dropdown by default', () => {
+    renderWithTheme(<ReportForm {...baseProps} />);
+    expect(screen.queryByTestId('format-dropdown')).not.toBeInTheDocument();
+  });
+
+  it('renders format dropdown when withFormat is true', () => {
+    renderWithTheme(<ReportForm {...baseProps} withFormat={true} setFormat={jest.fn()} />);
+    expect(screen.getByTestId('format-dropdown')).toBeInTheDocument();
+  });
+
+  it('passes the format value through to the dropdown', () => {
+    renderWithTheme(
+      <ReportForm {...baseProps} withFormat={true} format="excel" setFormat={jest.fn()} />
+    );
+    expect(screen.getByTestId('format-dropdown')).toHaveValue('excel');
+  });
+
+  it('calls setFormat when the format dropdown changes', () => {
+    const setFormat = jest.fn();
+    renderWithTheme(<ReportForm {...baseProps} withFormat={true} setFormat={setFormat} />);
+    fireEvent.change(screen.getByTestId('format-dropdown'), { target: { value: 'excel' } });
+    expect(setFormat).toHaveBeenCalledWith('excel');
+  });
+
   it('does not render delimiter dropdown when withDelimiter is false', () => {
     renderWithTheme(<ReportForm {...baseProps} withDelimiter={false} />);
     expect(screen.queryByTestId('delimiter-dropdown')).not.toBeInTheDocument();
diff --git a/src/components/ReportForm/ReportForm.tsx b/src/components/ReportForm/ReportForm.tsx
index 87d18998..71b8ec9b 100644
--- a/src/components/ReportForm/ReportForm.tsx
+++ b/src/components/ReportForm/ReportForm.tsx
@@ -7,6 +7,7 @@ import Button from '../Button';
 import LabeledComponent from '../LabeledComponent';
 import MonthDropdown from '../MonthDropdown';
 import DelimiterDropdown from './DelimiterDropdown';
+import FormatDropdown from './FormatDropdown';
 
 const StyledLabeledComponent = styled(LabeledComponent)`
   width: 50%;
@@ -52,10 +53,13 @@ const ReportForm = ({
   children,
   date,
   delimiter = ',',
+  format = 'pdf',
   withMonth = true,
   withDelimiter = true,
+  withFormat = false,
   setDate,
   setDelimiter,
+  setFormat,
   generate,
   parameters,
 }: {
@@ -63,10 +67,13 @@ const ReportForm = ({
   children?: React.ReactNode;
   date?: { year?: number | null; month?: number | null };
   delimiter?: string;
+  format?: string;
   withMonth?: boolean;
   withDelimiter?: boolean;
+  withFormat?: boolean;
   setDate: (date: any) => void;
   setDelimiter?: (delimiter: string) => void;
+  setFormat?: (format: string) => void;
   generate: (date: any, parameters: any) => void;
   parameters?: any;
 }) => {
@@ -95,6 +102,13 @@ const ReportForm = ({
     />
   )
 
+  const formatInput = (
+    <FormatDropdown
+      value={format}
+      onChange={setFormat}
+    />
+  )
+
   return (
     <form
       className="ReportForm"
@@ -104,6 +118,7 @@ const ReportForm = ({
         <StyledLabeledComponent label={t('report.year')} component={yearInput}/>
         {withMonth && <StyledLabeledComponent label={t('report.month')} component={monthInput}/>}
         {withDelimiter && <StyledLabeledComponent label={t('report.delimiter')} component={delimiterInput}/>}
+        {withFormat && <StyledLabeledComponent label={t('report.format')} component={formatInput}/>}
         {children}
         <Button
           type="submit"
@@ -124,10 +139,13 @@ ReportForm.propTypes = {
     month: PropTypes.number,
   }),
   delimiter: PropTypes.string,
+  format: PropTypes.string,
   withMonth: PropTypes.bool,
   withDelimiter: PropTypes.bool,
+  withFormat: PropTypes.bool,
   setDate: PropTypes.func.isRequired,
   setDelimiter: PropTypes.func,
+  setFormat: PropTypes.func,
   generate: PropTypes.func.isRequired,
 };
 
diff --git a/src/containers/InvoicesReportFormContainer.tsx b/src/containers/InvoicesReportFormContainer.tsx
index f41b9713..5d08f412 100644
--- a/src/containers/InvoicesReportFormContainer.tsx
+++ b/src/containers/InvoicesReportFormContainer.tsx
@@ -1,6 +1,6 @@
 import React, { useEffect } from 'react';
 import {connect} from 'react-redux';
-import {generateReport, initReport, setReportDate} from '../modules/reports';
+import {generateReport, initReport, setReportDate, setReportParameter} from '../modules/reports';
 import ReportForm from '../components/ReportForm';
 import {RootState} from '../modules';
 
@@ -12,9 +12,11 @@ interface ReportDate {
 interface Props {
   initialized: boolean;
   date?: ReportDate;
+  format?: string;
   generationInProgress?: boolean;
   initReport: () => void;
   setDate: (date: ReportDate) => void;
+  setFormat: (format: string) => void;
   generate: () => void;
 }
 
@@ -28,9 +30,12 @@ const InvoicesReportFormContainer = (props: Props) => {
     <ReportForm
       disabled={!props.initialized || props.generationInProgress}
       date={props.date}
+      format={props.format}
       setDate={props.setDate}
+      setFormat={props.setFormat}
       generate={props.generate}
       withDelimiter={false}
+      withFormat
     />
   );
 };
@@ -47,6 +52,7 @@ const mapStateToProps = (state: RootState) => {
   return {
     initialized,
     date: report.date,
+    format: report.parameters.format || 'pdf',
     generationInProgress: report.generationInProgress === true,
   };
 };
@@ -54,6 +60,8 @@ const mapStateToProps = (state: RootState) => {
 const mapDispatchToProps = (dispatch: any) => ({
   initReport: () => dispatch(initReport('invoices')),
   setDate: (date: any) => dispatch(setReportDate('invoices', date)),
+  setFormat: (format: string) =>
+    dispatch(setReportParameter('invoices', 'format', format)),
   generate: () => dispatch(generateReport('invoices')),
 });
 
diff --git a/src/containers/containers.spec.tsx b/src/containers/containers.spec.tsx
index a0365d3a..f9a50a09 100644
--- a/src/containers/containers.spec.tsx
+++ b/src/containers/containers.spec.tsx
@@ -90,10 +90,17 @@ jest.mock('../components/YearlySummaryReportForm', () => ({
   default: () => <div data-testid="yearly-summary-report-form" />,
 }));
 
-jest.mock('../components/ReportForm', () => ({
-  __esModule: true,
-  default: () => <div data-testid="report-form" />,
-}));
+// A jest.fn() wrapper (rather than a plain stub) so the invoices format
+// wiring test below can inspect the props InvoicesReportFormContainer passes
+// down and drive its setFormat callback directly.
+jest.mock('../components/ReportForm', () => {
+  const React = require('react');
+  const mockReportForm = jest.fn((_props: any) => React.createElement('div', {'data-testid': 'report-form'}));
+  return {
+    __esModule: true,
+    default: mockReportForm,
+  };
+});
 
 jest.mock('../components/AirstatReportForm', () => ({
   __esModule: true,
@@ -239,6 +246,42 @@ describe('container mount dispatches', () => {
     expect(inits[0].payload.name).toBe('invoices');
   });
 
+  it('InvoicesReportFormContainer defaults format to pdf when no parameter is set', () => {
+    const store = makeStore({ reports: { invoices: { date: {}, parameters: {} } } });
+    render(wrap(store, <InvoicesReportFormContainer />));
+    const ReportForm = require('../components/ReportForm').default;
+    const lastProps = ReportForm.mock.calls[ReportForm.mock.calls.length - 1][0];
+    expect(lastProps.format).toBe('pdf');
+    expect(lastProps.withFormat).toBe(true);
+  });
+
+  it('InvoicesReportFormContainer passes through a format already in state', () => {
+    const store = makeStore({
+      reports: { invoices: { date: {}, parameters: { format: 'excel' } } },
+    });
+    render(wrap(store, <InvoicesReportFormContainer />));
+    const ReportForm = require('../components/ReportForm').default;
+    const lastProps = ReportForm.mock.calls[ReportForm.mock.calls.length - 1][0];
+    expect(lastProps.format).toBe('excel');
+  });
+
+  it('InvoicesReportFormContainer dispatches SET_REPORT_PARAMETER when the format is changed', () => {
+    const store = makeStore({ reports: { invoices: { date: {}, parameters: {} } } });
+    render(wrap(store, <InvoicesReportFormContainer />));
+    const ReportForm = require('../components/ReportForm').default;
+    const lastProps = ReportForm.mock.calls[ReportForm.mock.calls.length - 1][0];
+
+    lastProps.setFormat('excel');
+
+    const paramActions = store.actions.filter(a => a.type === 'SET_REPORT_PARAMETER');
+    expect(paramActions).toHaveLength(1);
+    expect(paramActions[0].payload).toEqual({
+      report: 'invoices',
+      parameterName: 'format',
+      parameterValue: 'excel',
+    });
+  });
+
   it('AerodromeStatusBannerContainer dispatches WATCH_CURRENT_AERODROME_STATUS exactly once on mount', () => {
     const store = makeStore({
       settings: {
diff --git a/src/locales/de.json b/src/locales/de.json
index 30cf2376..34c8f837 100644
--- a/src/locales/de.json
+++ b/src/locales/de.json
@@ -377,7 +377,7 @@
   "adminExport": {
     "bazlReport": "BAZL-Report herunterladen (CSV)",
     "landingList": "Landeliste herunterladen (CSV)",
-    "invoiceReports": "Rechnungsberichte herunterladen (PDF)",
+    "invoiceReports": "Rechnungsberichte herunterladen",
     "yearlySummary": "Jahreszusammenfassung herunterladen (CSV)"
   },
   "adminAircraft": {
@@ -432,7 +432,8 @@
   "report": {
     "year": "Jahr",
     "month": "Monat",
-    "delimiter": "Trennzeichen"
+    "delimiter": "Trennzeichen",
+    "format": "Format"
   },
   "yearlySummary": {
     "intro": "Die Jahreszusammenfassung enthält für jeden Monat des Jahres eine Zeile mit den folgenden Informationen:",
@@ -602,6 +603,9 @@
     "colEmail": "E-Mail",
     "colDirection": "Einflug / Ausflug",
     "directionArrival": "Einflug",
-    "directionDeparture": "Ausflug"
+    "directionDeparture": "Ausflug",
+    "formatPdf": "PDF",
+    "formatExcel": "Excel",
+    "sheetNameFallback": "Rechnungsempfänger"
   }
 }
diff --git a/src/locales/en.json b/src/locales/en.json
index 3ae5e976..33cc8144 100644
--- a/src/locales/en.json
+++ b/src/locales/en.json
@@ -377,7 +377,7 @@
   "adminExport": {
     "bazlReport": "Download FOCA report (CSV)",
     "landingList": "Download landing list (CSV)",
-    "invoiceReports": "Download invoice reports (PDF)",
+    "invoiceReports": "Download invoice reports",
     "yearlySummary": "Download yearly summary (CSV)"
   },
   "adminAircraft": {
@@ -432,7 +432,8 @@
   "report": {
     "year": "Year",
     "month": "Month",
-    "delimiter": "Delimiter"
+    "delimiter": "Delimiter",
+    "format": "Format"
   },
   "yearlySummary": {
     "intro": "The yearly summary contains one row per month with the following information:",
@@ -602,6 +603,9 @@
     "colEmail": "Email",
     "colDirection": "Arrival / Departure",
     "directionArrival": "Arrival",
-    "directionDeparture": "Departure"
+    "directionDeparture": "Departure",
+    "formatPdf": "PDF",
+    "formatExcel": "Excel",
+    "sheetNameFallback": "Invoice recipient"
   }
 }
diff --git a/src/modules/reports/sagas.spec.ts b/src/modules/reports/sagas.spec.ts
index 9bfc3e09..2c639912 100644
--- a/src/modules/reports/sagas.spec.ts
+++ b/src/modules/reports/sagas.spec.ts
@@ -5,10 +5,13 @@ import * as sagas from './sagas';
 jest.mock('../../util/report', () => ({
   airstat: jest.fn(),
   invoices: jest.fn(),
+  invoicesExcel: jest.fn(),
   landings: jest.fn(),
   yearlySummary: jest.fn(),
 }));
 
+jest.mock('../../util/downloadBlob', () => jest.fn());
+
 describe('modules', () => {
   describe('reports', () => {
     describe('sagas', () => {
@@ -105,6 +108,134 @@ describe('modules', () => {
         });
       });
 
+      describe('generateReport (xlsx path - invoices)', () => {
+        it('should generate and download an xlsx report when format is excel', () => {
+          const report = 'invoices';
+          const action = actions.generateReport(report);
+          const generator = sagas.generateReport(action);
+
+          expect(generator.next().value).toEqual(
+            put(actions.setReportGenerationInProgress(report, true))
+          );
+
+          // select
+          generator.next();
+
+          const reportState = {
+            date: {year: 2024, month: 11},
+            parameters: {format: 'excel'}
+          };
+
+          const blob = {size: 1234};
+          const download = {
+            type: 'xlsx',
+            filename: 'invoice_recipients_2024_11.xlsx',
+            result: blob
+          };
+
+          expect(generator.next(reportState).value).toMatchObject({
+            type: 'CALL'
+          });
+
+          expect(generator.next(download).value).toEqual(
+            put(actions.setReportGenerationInProgress(report, false))
+          );
+
+          const downloadEffect = generator.next().value;
+          expect(downloadEffect).toMatchObject({type: 'CALL'});
+          expect((downloadEffect as any).payload.args).toEqual([
+            'invoice_recipients_2024_11.xlsx',
+            blob
+          ]);
+
+          expect(generator.next().done).toEqual(true);
+        });
+
+        it('drives the inner generator to an xlsx descriptor for format=excel', () => {
+          // The two tests above simulate generate()'s return value; this one
+          // actually runs generate()'s switch/case to the end, so the filename
+          // template and the excel/pdf branch choice are genuinely exercised.
+          const {invoices, invoicesExcel} = require('../../util/report');
+          const blob = {size: 1};
+          const generator = sagas.generateReport(actions.generateReport('invoices'));
+
+          generator.next();
+          generator.next();
+
+          const callEffect = generator.next({
+            date: {year: 2024, month: 11},
+            parameters: {format: 'excel'}
+          }).value;
+
+          const inner = (callEffect as any).payload.fn(
+            'invoices', 2024, 11, {format: 'excel'}
+          );
+          const innerCallEffect = inner.next().value;
+          expect(innerCallEffect.payload.fn).toBe(invoicesExcel);
+          expect(innerCallEffect.payload.args).toEqual([2024, 11, {format: 'excel'}]);
+
+          const {value: result, done} = inner.next(blob);
+          expect(done).toBe(true);
+          expect(result).toEqual({
+            type: 'xlsx',
+            filename: 'invoice_recipients_2024_11.xlsx',
+            result: blob
+          });
+          expect(invoices).not.toHaveBeenCalled();
+        });
+
+        it('drives the inner generator to a pdf descriptor when no format is set', () => {
+          const {invoices, invoicesExcel} = require('../../util/report');
+          const pdfResult = {download: jest.fn()};
+          const generator = sagas.generateReport(actions.generateReport('invoices'));
+
+          generator.next();
+          generator.next();
+
+          const callEffect = generator.next({
+            date: {year: 2024, month: 11},
+            parameters: {}
+          }).value;
+
+          const inner = (callEffect as any).payload.fn('invoices', 2024, 11, {});
+          const innerCallEffect = inner.next().value;
+          expect(innerCallEffect.payload.fn).toBe(invoices);
+
+          const {value: result, done} = inner.next(pdfResult);
+          expect(done).toBe(true);
+          expect(result).toEqual({
+            type: 'pdf',
+            filename: 'invoice_recipients_2024_11.pdf',
+            result: pdfResult
+          });
+          expect(invoicesExcel).not.toHaveBeenCalled();
+        });
+      });
+
+      describe('generateReport (failure)', () => {
+        it('clears the in-progress flag when generation fails', () => {
+          const report = 'invoices';
+          const generator = sagas.generateReport(actions.generateReport(report));
+
+          expect(generator.next().value).toEqual(
+            put(actions.setReportGenerationInProgress(report, true))
+          );
+
+          // select
+          generator.next();
+
+          // generate call
+          generator.next({date: {year: 2024, month: 11}, parameters: {format: 'excel'}});
+
+          // A failure must not leave the form disabled forever.
+          expect(generator.throw(new Error('customs down')).value).toEqual(
+            put(actions.setReportGenerationInProgress(report, false))
+          );
+
+          expect(() => generator.next()).toThrow('customs down');
+        });
+      });
+
       describe('generateReport (csv path - landings)', () => {
         it('should generate and download a landings csv report', () => {
           const report = 'landings';
diff --git a/src/modules/reports/sagas.ts b/src/modules/reports/sagas.ts
index ef7aefc3..f15ca810 100644
--- a/src/modules/reports/sagas.ts
+++ b/src/modules/reports/sagas.ts
@@ -1,6 +1,7 @@
 import {all, call, put, select, takeEvery} from 'redux-saga/effects';
 import * as actions from './actions';
-import {airstat, invoices, landings, yearlySummary} from '../../util/report';
+import {airstat, invoices, invoicesExcel, landings, yearlySummary} from '../../util/report';
+import downloadBlob from '../../util/downloadBlob';
 
 export const selectReport = (report: string) => (state: any) => state.reports[report];
 
@@ -16,6 +17,13 @@ function* generate(report: string, year: number, month: number, options: unknown
       const yearlySummaryResult = yield call(yearlySummary, year, options)
       return csv(yearlySummaryResult);
     case 'invoices':
+      if ((options as any)?.format === 'excel') {
+        const invoicesExcelResult = yield call(invoicesExcel, year, month, options)
+        return xlsx(
+          `invoice_recipients_${year}_${month}.xlsx`,
+          invoicesExcelResult
+        )
+      }
       const invoicesResult = yield call(invoices, year, month, options)
       return pdf(
         `invoice_recipients_${year}_${month}.pdf`,
@@ -41,6 +49,14 @@ function pdf(filename: string, result: unknown) {
   }
 }
 
+function xlsx(filename: string, result: unknown) {
+  return {
+    type: 'xlsx',
+    filename,
+    result
+  }
+}
+
 function* startDownload(download: any) {
   download.start();
 }
@@ -55,14 +71,20 @@ export function* generateReport(action: any) {
   const year = state.date.year;
   const month = state.date.month;
 
-  const download = yield call(generate, report, year, month, state.parameters);
-
-  yield put(actions.setReportGenerationInProgress(report, false));
+  let download;
+  try {
+    download = yield call(generate, report, year, month, state.parameters);
+  } finally {
+    // Always clear the flag: a failed report must not leave the form disabled.
+    yield put(actions.setReportGenerationInProgress(report, false));
+  }
 
   if (download.type === 'csv') {
     yield call(startDownload, download.result);
   } else if (download.type === 'pdf') {
     download.result.download(download.filename)
+  } else if (download.type === 'xlsx') {
+    yield call(downloadBlob, download.filename, download.result)
   } else {
     throw new Error('Unsupported type ' + download.type)
   }
diff --git a/src/util/InvoicesExcelReport.spec.ts b/src/util/InvoicesExcelReport.spec.ts
new file mode 100644
index 00000000..5b84cd38
--- /dev/null
+++ b/src/util/InvoicesExcelReport.spec.ts
@@ -0,0 +1,533 @@
+// A non-UTC timezone, so that any local-time arithmetic in the date handling
+// would show up as an off-by-one day rather than passing by coincidence.
+process.env.TZ = 'America/New_York';
+
+describe('util', () => {
+  describe('InvoicesExcelReport', () => {
+    let InvoicesExcelReport;
+    let sanitizeSheetName;
+    let columnLetter;
+    let toDateValue;
+
+    beforeEach(() => {
+      global.__CONF__ = {
+        aerodrome: {
+          ICAO: 'LSZT',
+          runways: [
+            {name: '10', type: 'A'},
+            {name: '28', type: 'A'},
+          ],
+        },
+        enabledFlightTypes: {0: 'private', 1: 'instruction'},
+        memberManagement: false,
+      };
+
+      jest.resetModules();
+      jest.mock('./firebase');
+      jest.mock('firebase/database', () => ({
+        get: jest.fn(),
+        query: jest.fn(ref => ref),
+        orderByChild: jest.fn(),
+        startAt: jest.fn(),
+        endAt: jest.fn(),
+      }));
+
+      const module = require('./InvoicesExcelReport');
+      InvoicesExcelReport = module.default;
+      sanitizeSheetName = module.sanitizeSheetName;
+      columnLetter = module.columnLetter;
+      toDateValue = module.toDateValue;
+    });
+
+    const makeReport = (year = 2023, month = 6, options = {}) =>
+      new InvoicesExcelReport(year, month, options);
+
+    const arrival = (overrides = {}) => Object.assign({
+      date: '2023-06-01',
+      time: '10:00',
+      immatriculation: 'HB-KOF',
+      mtow: 750,
+      firstname: 'Max',
+      lastname: 'Muster',
+      email: 'max@example.com',
+      flightType: 'private',
+      feeTotalNet: 10,
+      feeVat: 1,
+      feeRoundingDifference: 0,
+      feeTotalGross: 11,
+    }, overrides);
+
+    const declaration = (overrides = {}) => Object.assign({
+      date: '2023-06-01',
+      registration: 'HB-KOF',
+      email: 'max@example.com',
+      direction: 'arrival',
+      fee: {totalNet: 10, vat: 1, roundingDifference: 0, totalGrossRounded: 11},
+    }, overrides);
+
+    let lastBuffer: any = null;
+
+    /**
+     * Render the sheets to a real xlsx buffer and read it back, so assertions
+     * are made against what actually lands in the file.
+     */
+    async function render(report, recipientNames, arrivalRecipients = {}, customsRecipients = {}) {
+      const {Workbook} = require('exceljs');
+      const workbook = new Workbook();
+      workbook.calcProperties.fullCalcOnLoad = true;
+
+      report.addSheets(workbook, recipientNames, arrivalRecipients, customsRecipients);
+
+      lastBuffer = await workbook.xlsx.writeBuffer();
+      const reloaded = new Workbook();
+      await reloaded.xlsx.load(lastBuffer);
+      return reloaded;
+    }
+
+    /**
+     * The formula cells of a rendered sheet, read straight out of the xlsx XML.
+     *
+     * exceljs's own reader reports a cached result of 0 as undefined, which
+     * would hide whether zero totals actually reach the file — and a zero total
+     * read as blank is exactly the failure the cached results exist to prevent.
+     */
+    async function writtenFormulas(sheetIndex = 1) {
+      const JSZip = require('jszip');
+      const zip = await JSZip.loadAsync(lastBuffer);
+      const xml = await zip.file(`xl/worksheets/sheet${sheetIndex}.xml`).async('string');
+
+      const cells: any[] = [];
+      const pattern = /<c r="([A-Z]+\d+)"[^>]*><f>([^<]*)<\/f><v>([^<]*)<\/v><\/c>/g;
+      let match;
+      while ((match = pattern.exec(xml)) !== null) {
+        cells.push({ref: match[1], formula: match[2], result: Number(match[3])});
+      }
+      return cells;
+    }
+
+    /** The row whose first cell matches the given text. */
+    function rowStartingWith(sheet, text) {
+      let found: any = null;
+      sheet.eachRow(row => {
+        if (!found && row.getCell(1).value === text) {
+          found = row;
+        }
+      });
+      return found;
+    }
+
+    describe('columnLetter', () => {
+      it('maps the first columns to A, B, C', () => {
+        expect(columnLetter(1)).toBe('A');
+        expect(columnLetter(2)).toBe('B');
+        expect(columnLetter(3)).toBe('C');
+      });
+
+      it('maps the last landing fee column to L', () => {
+        expect(columnLetter(12)).toBe('L');
+      });
+
+      it('rolls over past Z', () => {
+        expect(columnLetter(26)).toBe('Z');
+        expect(columnLetter(27)).toBe('AA');
+        expect(columnLetter(28)).toBe('AB');
+      });
+    });
+
+    describe('toDateValue', () => {
+      it('converts a local date string to a UTC date', () => {
+        const value = toDateValue('2023-06-01');
+        expect(value).toBeInstanceOf(Date);
+        expect(value.getUTCFullYear()).toBe(2023);
+        expect(value.getUTCMonth()).toBe(5);
+        expect(value.getUTCDate()).toBe(1);
+      });
+
+      it('passes through values that are not plain local dates', () => {
+        expect(toDateValue('2023-06-01T10:00:00Z')).toBe('2023-06-01T10:00:00Z');
+        expect(toDateValue(undefined)).toBeUndefined();
+        expect(toDateValue(42)).toBe(42);
+      });
+    });
+
+    describe('sanitizeSheetName', () => {
+      it('keeps an ordinary name unchanged', () => {
+        expect(sanitizeSheetName('Company A')).toBe('Company A');
+      });
+
+      it('replaces the characters Excel forbids', () => {
+        expect(sanitizeSheetName('A/B:C*D?E[F]G\\H')).toBe('A B C D E F G H');
+      });
+
+      it('truncates to 31 characters', () => {
+        const name = sanitizeSheetName('x'.repeat(50));
+        expect(name).toHaveLength(31);
+      });
+
+      it('falls back when the name is empty after cleaning', () => {
+        expect(sanitizeSheetName('///')).toBe('Rechnungsempfänger');
+        expect(sanitizeSheetName('')).toBe('Rechnungsempfänger');
+      });
+
+      it('de-duplicates against names already used', () => {
+        expect(sanitizeSheetName('Company A', ['Company A'])).toBe('Company A (2)');
+        expect(sanitizeSheetName('Company A', ['Company A', 'Company A (2)']))
+          .toBe('Company A (3)');
+      });
+
+      it('keeps a de-duplicated long name within the length limit', () => {
+        const base = sanitizeSheetName('y'.repeat(50));
+        const name = sanitizeSheetName('y'.repeat(50), [base]);
+        expect(name.length).toBeLessThanOrEqual(31);
+        expect(name.endsWith(' (2)')).toBe(true);
+      });
+
+      it('de-duplicates case-insensitively, as Excel does', () => {
+        // exceljs rejects names differing only in case, which would abort the
+        // whole report.
+        expect(sanitizeSheetName('flugschule ag', ['Flugschule AG']))
+          .toBe('flugschule ag (2)');
+      });
+
+      it('strips leading and trailing single quotes', () => {
+        expect(sanitizeSheetName("'Air Service'")).toBe('Air Service');
+      });
+
+      it('strips a quote that was already at the edge before truncation', () => {
+        const name = sanitizeSheetName('x'.repeat(30) + "''''");
+        expect(name.endsWith("'")).toBe(false);
+      });
+
+      it('strips a quote that truncation newly exposes at the edge', () => {
+        // The quote sits mid-string in the original name, so the first trim
+        // pass leaves it alone; only cutting at 31 chars lands exactly on it.
+        const name = 'x'.repeat(30) + "'" + 'y'.repeat(5);
+        expect(name.length).toBeGreaterThan(31);
+        expect(name.substring(0, 31).endsWith("'")).toBe(true);
+
+        const result = sanitizeSheetName(name);
+        expect(result.endsWith("'")).toBe(false);
+      });
+
+      it('avoids the reserved name History', () => {
+        expect(sanitizeSheetName('History')).not.toBe('History');
+      });
+
+      it('falls back for a nullish name', () => {
+        expect(sanitizeSheetName(null as any)).toBe('Rechnungsempfänger');
+        expect(sanitizeSheetName(undefined as any)).toBe('Rechnungsempfänger');
+      });
+
+      it('falls back when the cleaned name survives but collapses to nothing after the final quote trim', () => {
+        // The forbidden-character strip leaves the surrounding spaces alone (a
+        // quote is not a forbidden character), so the first trim only removes
+        // whitespace and 'cleaned' comes out as a lone quote — non-empty, so
+        // the fallback used while building 'base' is skipped. Only the very
+        // last trim (after substring) reduces it to '', which is what the
+        // final `|| fallback` exists to catch.
+        expect(sanitizeSheetName("  '  ")).toBe('Rechnungsempfänger');
+      });
+
+      it('distinguishes names that collide only after truncation', () => {
+        const first = sanitizeSheetName('z'.repeat(31) + 'AAA');
+        const second = sanitizeSheetName('z'.repeat(31) + 'BBB', [first]);
+        expect(second).not.toBe(first);
+      });
+    });
+
+    describe('addSheets', () => {
+      it('adds one sheet per recipient, in the given order', async () => {
+        const report = makeReport();
+        const workbook = await render(report, ['Online-Zahlungen', 'Company A'], {
+          'Company A': [arrival()],
+        });
+        expect(workbook.worksheets.map(sheet => sheet.name))
+          .toEqual(['Online-Zahlungen', 'Company A']);
+      });
+
+      it('titles each sheet with the recipient and month', async () => {
+        const report = makeReport(2023, 6);
+        const workbook = await render(report, ['Company A'], {'Company A': [arrival()]});
+        expect(workbook.getWorksheet('Company A').getCell('A1').value)
+          .toBe('Company A (Juni 2023)');
+      });
+
+      it('uses the untruncated recipient name in the title even when the sheet name is cut', async () => {
+        const longName = 'A very long invoice recipient name indeed';
+        const report = makeReport();
+        const workbook = await render(report, [longName], {[longName]: [arrival()]});
+        const sheet = workbook.worksheets[0];
+        expect(sheet.name.length).toBeLessThanOrEqual(31);
+        expect(sheet.getCell('A1').value).toContain(longName);
+      });
+
+      it('gives colliding recipient names distinct sheets', async () => {
+        const report = makeReport();
+        const workbook = await render(report, ['A/B', 'A:B'], {
+          'A/B': [arrival()],
+          'A:B': [arrival()],
+        });
+        const names = workbook.worksheets.map(sheet => sheet.name);
+        expect(new Set(names).size).toBe(2);
+      });
+
+      it('survives recipient names that Excel would reject', async () => {
+        // Recipient names are user-controlled; any of these makes exceljs throw
+        // if it reaches addWorksheet unsanitised, which would abort the report.
+        const names = [
+          'History',
+          "'Air Service'",
+          'Flugschule AG',
+          'flugschule ag',
+          'A/B:C*D?E[F]',
+          'A very long invoice recipient name that goes on and on',
+          '',
+        ];
+        const report = makeReport();
+        const arrivalRecipients = {};
+        names.forEach(name => { arrivalRecipients[name] = [arrival()]; });
+
+        const workbook = await render(report, names, arrivalRecipients);
+
+        const sheetNames = workbook.worksheets.map(sheet => sheet.name);
+        expect(sheetNames).toHaveLength(names.length);
+        expect(new Set(sheetNames.map(n => n.toLowerCase())).size).toBe(names.length);
+        sheetNames.forEach(name => {
+          expect(name.length).toBeLessThanOrEqual(31);
+          expect(name).not.toBe('History');
+          expect(/[[\]:*?/\\]/.test(name)).toBe(false);
+          expect(/(^')|('$)/.test(name)).toBe(false);
+        });
+      });
+
+      it('writes a fallback sheet with the no-recipients message', async () => {
+        const report = makeReport(2023, 6);
+        const workbook = await render(report, []);
+        expect(workbook.worksheets).toHaveLength(1);
+        expect(workbook.worksheets[0].getCell('A1').value)
+          .toContain('Keine Rechnungsempfänger');
+      });
+
+      it('still adds a sheet for a recipient with no rows', async () => {
+        const report = makeReport();
+        const workbook = await render(report, ['Online-Zahlungen']);
+        expect(workbook.worksheets.map(sheet => sheet.name)).toEqual(['Online-Zahlungen']);
+        expect(await writtenFormulas()).toHaveLength(0);
+      });
+    });
+
+    describe('landing fees table', () => {
+      it('writes amounts as numbers, not formatted strings', async () => {
+        const report = makeReport();
+        const workbook = await render(report, ['Company A'], {
+          'Company A': [arrival({feeTotalNet: 14.5, feeVat: 1.2, feeRoundingDifference: 0.3, feeTotalGross: 16})],
+        });
+        const sheet = workbook.getWorksheet('Company A');
+        const dataRow = sheet.getRow(5);
+        expect(typeof dataRow.getCell(9).value).toBe('number');
+        expect(dataRow.getCell(9).value).toBe(14.5);
+        expect(dataRow.getCell(12).value).toBe(16);
+        expect(dataRow.getCell(12).numFmt).toBe('#,##0.00');
+      });
+
+      it('writes the date as a real date on the intended calendar day', async () => {
+        const report = makeReport();
+        const workbook = await render(report, ['Company A'], {
+          'Company A': [arrival({date: '2023-06-01'})],
+        });
+        const sheet = workbook.getWorksheet('Company A');
+        const dateCell = sheet.getRow(5).getCell(1);
+        expect(dateCell.value).toBeInstanceOf(Date);
+        expect(dateCell.value.toISOString().substring(0, 10)).toBe('2023-06-01');
+      });
+
+      it('totals each amount column with a SUM formula carrying a cached result', async () => {
+        const report = makeReport();
+        const workbook = await render(report, ['Company A'], {
+          'Company A': [
+            arrival({feeTotalNet: 10, feeVat: 1, feeRoundingDifference: 0, feeTotalGross: 11}),
+            arrival({feeTotalNet: 20, feeVat: 2, feeRoundingDifference: 0, feeTotalGross: 22}),
+          ],
+        });
+        const totals = await writtenFormulas();
+
+        expect(totals).toHaveLength(4);
+        expect(totals.map(cell => cell.result)).toEqual([30, 3, 0, 33]);
+        totals.forEach(cell => {
+          expect(cell.formula).toMatch(/^SUM\([A-Z]+\d+:[A-Z]+\d+\)$/);
+        });
+      });
+
+      it('sums exactly the rows of its own table', async () => {
+        const report = makeReport();
+        await render(report, ['Company A'], {
+          'Company A': [arrival(), arrival()],
+        });
+        // Title (1), spacer (2), subheader (3), header (4), two data rows (5-6).
+        expect((await writtenFormulas())[0].formula).toBe('SUM(I5:I6)');
+      });
+
+      it('leaves net, VAT and rounding empty for transition-month rows', async () => {
+        const report = makeReport();
+        const workbook = await render(report, ['Company A'], {
+          'Company A': [arrival({
+            feeTotalNet: undefined,
+            feeVat: undefined,
+            feeRoundingDifference: undefined,
+            feeTotalGross: undefined,
+            landingFeeTotal: 20,
+          })],
+        });
+        const sheet = workbook.getWorksheet('Company A');
+        const dataRow = sheet.getRow(5);
+
+        expect(dataRow.getCell(9).value).toBeNull();
+        expect(dataRow.getCell(10).value).toBeNull();
+        expect(dataRow.getCell(11).value).toBeNull();
+        expect(dataRow.getCell(12).value).toBe(20);
+      });
+
+      it('keeps cached totals consistent with SUM over blanks in the transition month', async () => {
+        const report = makeReport();
+        const workbook = await render(report, ['Company A'], {
+          'Company A': [
+            arrival({
+              feeTotalNet: undefined, feeVat: undefined,
+              feeRoundingDifference: undefined, feeTotalGross: undefined,
+              landingFeeTotal: 20,
+            }),
+            arrival({feeTotalNet: 10, feeVat: 1, feeRoundingDifference: 0, feeTotalGross: 11}),
+          ],
+        });
+        const totals = await writtenFormulas();
+        // SUM ignores the blank cells, matching the JS accumulation exactly.
+        expect(totals.map(cell => cell.result)).toEqual([10, 1, 0, 31]);
+      });
+    });
+
+    describe('malformed amounts', () => {
+      it('writes no total at all rather than NaN when an amount is missing', async () => {
+        const report = makeReport();
+        await render(report, ['Company A'], {
+          'Company A': [arrival({
+            feeTotalNet: undefined, feeVat: undefined,
+            feeRoundingDifference: undefined, feeTotalGross: undefined,
+            landingFeeTotal: undefined,
+          })],
+        });
+        const totals = await writtenFormulas();
+        // A NaN here would make Excel report the workbook as corrupt.
+        totals.forEach(cell => expect(Number.isNaN(cell.result)).toBe(false));
+        expect(totals.map(cell => cell.result)).toEqual([0, 0, 0, 0]);
+      });
+
+      it('does not let one malformed row poison the column total', async () => {
+        const report = makeReport();
+        await render(report, ['Company A'], {
+          'Company A': [
+            arrival({feeTotalGross: undefined, landingFeeTotal: undefined}),
+            arrival({feeTotalNet: 10, feeVat: 1, feeRoundingDifference: 0, feeTotalGross: 11}),
+          ],
+        });
+        expect((await writtenFormulas()).map(cell => cell.result)).toEqual([10, 1, 0, 11]);
+      });
+
+      it('survives a customs declaration with no fee', async () => {
+        const report = makeReport();
+        await render(report, ['Company A'], {}, {
+          'Company A': [declaration({fee: undefined})],
+        });
+        expect((await writtenFormulas()).map(cell => cell.result)).toEqual([0, 0, 0, 0]);
+      });
+    });
+
+    describe('customs fees tables', () => {
+      it('writes cancelled and non-cancelled declarations to separate tables', async () => {
+        const report = makeReport();
+        const workbook = await render(report, ['Company A'], {}, {
+          'Company A': [declaration(), declaration({cancelled: true})],
+        });
+        const sheet = workbook.getWorksheet('Company A');
+
+        expect(rowStartingWith(sheet, 'Zollgebühren')).not.toBeNull();
+        expect(rowStartingWith(sheet, 'Zollgebühren ANNULLIERT')).not.toBeNull();
+        // Four total columns per table, two tables.
+        expect(await writtenFormulas()).toHaveLength(8);
+      });
+
+      it('omits the cancelled table when nothing is cancelled', async () => {
+        const report = makeReport();
+        const workbook = await render(report, ['Company A'], {}, {
+          'Company A': [declaration()],
+        });
+        const sheet = workbook.getWorksheet('Company A');
+        expect(rowStartingWith(sheet, 'Zollgebühren ANNULLIERT')).toBeNull();
+        expect(await writtenFormulas()).toHaveLength(4);
+      });
+
+      it('handles a numeric fee as a transition-month fallback', async () => {
+        const report = makeReport();
+        await render(report, ['Company A'], {}, {
+          'Company A': [declaration({fee: 15})],
+        });
+        const totals = await writtenFormulas();
+        expect(totals.map(cell => cell.result)).toEqual([0, 0, 0, 15]);
+      });
+
+      it('translates the direction', async () => {
+        const report = makeReport();
+        const workbook = await render(report, ['Company A'], {}, {
+          'Company A': [declaration({direction: 'departure'})],
+        });
+        const sheet = workbook.getWorksheet('Company A');
+        expect(sheet.getRow(5).getCell(4).value).toBe('Ausflug');
+      });
+    });
+
+    describe('build', () => {
+      it('resolves with an xlsx blob', async () => {
+        const report = makeReport();
+        const blob = await report.build({
+          recipientNames: ['Company A'],
+          arrivalRecipients: {'Company A': [arrival()]},
+          customsRecipients: {},
+        });
+        expect(blob).toBeInstanceOf(Blob);
+        expect(blob.type)
+          .toBe('application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
+        expect(blob.size).toBeGreaterThan(0);
+      });
+
+      it('marks the workbook for full recalculation on load', async () => {
+        const {Workbook} = require('exceljs');
+        const report = makeReport();
+        const workbook = new Workbook();
+        workbook.calcProperties.fullCalcOnLoad = true;
+        report.addSheets(workbook, ['Company A'], {'Company A': [arrival()]}, {});
+        expect(workbook.calcProperties.fullCalcOnLoad).toBe(true);
+      });
+    });
+
+    describe('generate', () => {
+      it('resolves with the blob once the data is collected', async () => {
+        const report = makeReport();
+        report.collect = jest.fn().mockResolvedValue({
+          recipientNames: ['Company A'],
+          arrivalRecipients: {'Company A': [arrival()]},
+          customsRecipients: {},
+        });
+
+        await expect(report.generate()).resolves.toBeInstanceOf(Blob);
+      });
+
+      it('rejects when the data cannot be collected', async () => {
+        const report = makeReport();
+        report.collect = jest.fn().mockRejectedValue(new Error('customs down'));
+
+        // A silently swallowed failure would leave the form stuck showing the
+        // report as still being generated.
+        await expect(report.generate()).rejects.toThrow('customs down');
+      });
+    });
+  });
+});
diff --git a/src/util/InvoicesExcelReport.ts b/src/util/InvoicesExcelReport.ts
new file mode 100644
index 00000000..18efeb7a
--- /dev/null
+++ b/src/util/InvoicesExcelReport.ts
@@ -0,0 +1,360 @@
+import InvoicesReportData from './InvoicesReportData';
+import dates from '../util/dates';
+import {getLabel as getFlightTypeLabel} from '../util/flightTypes';
+import i18n from '../i18n';
+import loadWorkbookConstructor from './loadExcelJs';
+
+const t = i18n.getFixedT('de');
+
+export const XLSX_MIME_TYPE =
+  'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet';
+
+const MONEY_FORMAT = '#,##0.00';
+const DATE_FORMAT = 'dd.mm.yyyy';
+
+// Excel rejects these characters in worksheet names and caps them at 31 chars.
+const FORBIDDEN_SHEET_NAME_CHARS = /[[\]:*?/\\]/g;
+const MAX_SHEET_NAME_LENGTH = 31;
+// A worksheet name may not start or end with a single quote, and 'History' is
+// reserved. exceljs throws on all of these, which would abort the whole report.
+const EDGE_QUOTES = /^'+|'+$/g;
+const RESERVED_SHEET_NAME = 'History';
+
+const LOCAL_DATE_PATTERN = /^(\d{4})-(\d{2})-(\d{2})$/;
+
+interface Column {
+  header: string;
+  width: number;
+  numFmt?: string;
+  /** Whether the table's totals row sums this column. */
+  total?: boolean;
+}
+
+/**
+ * Convert a 1-based column index to its spreadsheet letter (1 -> A, 27 -> AA).
+ */
+export const columnLetter = (index: number): string => {
+  let letter = '';
+  let remaining = index;
+  while (remaining > 0) {
+    letter = String.fromCharCode(65 + ((remaining - 1) % 26)) + letter;
+    remaining = Math.floor((remaining - 1) / 26);
+  }
+  return letter;
+};
+
+/**
+ * Turn a local `YYYY-MM-DD` date into a real date cell value. Built in UTC so
+ * the writer's timezone can never shift it onto the neighbouring day. Anything
+ * that is not a plain local date is passed through as-is.
+ */
+export const toDateValue = (localDate: any): any => {
+  if (typeof localDate !== 'string') {
+    return localDate;
+  }
+  const match = LOCAL_DATE_PATTERN.exec(localDate);
+  if (!match) {
+    return localDate;
+  }
+  const [, year, month, day] = match;
+  return new Date(Date.UTC(Number(year), Number(month) - 1, Number(day)));
+};
+
+/**
+ * Make a recipient name usable as a worksheet name: drop the characters Excel
+ * forbids, keep it within the length limit, and disambiguate against the names
+ * already used in this workbook. Recipient names are user-controlled, so none
+ * of these can be assumed away.
+ */
+export const sanitizeSheetName = (name: string, usedNames: string[] = []): string => {
+  const trim = (value: string) => value.replace(EDGE_QUOTES, '').trim();
+
+  const cleaned = trim(
+    String(name == null ? '' : name).replace(FORBIDDEN_SHEET_NAME_CHARS, ' ')
+  );
+
+  // Truncating can expose a new trailing quote, so trim again afterwards.
+  const base = trim(
+    (cleaned || t('invoicesReport.sheetNameFallback')).substring(0, MAX_SHEET_NAME_LENGTH)
+  ) || t('invoicesReport.sheetNameFallback');
+
+  // exceljs compares worksheet names case-insensitively, so the check has to.
+  const isTaken = (candidate: string) =>
+    candidate === RESERVED_SHEET_NAME ||
+    usedNames.some(used => used.toLowerCase() === candidate.toLowerCase());
+
+  if (!isTaken(base)) {
+    return base;
+  }
+
+  for (let counter = 2; ; counter++) {
+    const suffix = ` (${counter})`;
+    const candidate =
+      base.substring(0, MAX_SHEET_NAME_LENGTH - suffix.length).trim() + suffix;
+    if (!isTaken(candidate)) {
+      return candidate;
+    }
+  }
+};
+
+/**
+ * Amounts reach a numeric cell verbatim, so anything that is not a finite
+ * number becomes an empty cell instead. A NaN would otherwise be written as
+ * `<v>NaN</v>`, which Excel reports as a corrupt workbook, and a single bad row
+ * would poison its column's total.
+ */
+const toAmount = (value: any): number | null =>
+  typeof value === 'number' && isFinite(value) ? value : null;
+
+const addAmounts = (totals: number[], amounts: (number | null)[]) => {
+  amounts.forEach((amount, index) => {
+    if (amount !== null) {
+      totals[index] += amount;
+    }
+  });
+};
+
+/**
+ * The invoice recipient report as an Excel workbook: one worksheet per
+ * recipient, mirroring the one-page-per-recipient layout of the PDF version.
+ *
+ * Unlike the PDF, amounts are written as real numbers and every totals row is a
+ * SUM formula, so recipients can filter, correct and re-sum rows in place. Each
+ * formula also carries its computed result as a cached value, because tools
+ * that do not evaluate formulas (pandas/openpyxl read with `data_only=True`)
+ * otherwise read those cells as empty.
+ */
+class InvoicesExcelReport extends InvoicesReportData {
+
+  /**
+   * Resolves with the workbook as a blob. Rejections propagate to the caller so
+   * a failure cannot leave the report stuck as "in progress".
+   */
+  generate(): Promise<Blob> {
+    return this.collect().then(data => this.build(data));
+  }
+
+  async build({recipientNames, arrivalRecipients, customsRecipients}) {
+    const Workbook = await loadWorkbookConstructor();
+
+    const workbook = new Workbook();
+    workbook.created = this.creationDate.toDate();
+    // Recalculate on open so the totals can never be shown from a stale cache.
+    workbook.calcProperties.fullCalcOnLoad = true;
+
+    this.addSheets(workbook, recipientNames, arrivalRecipients, customsRecipients);
+
+    const buffer = await workbook.xlsx.writeBuffer();
+
+    return new Blob([buffer], {type: XLSX_MIME_TYPE});
+  }
+
+  addSheets(workbook, recipientNames, arrivalRecipients, customsRecipients) {
+    if (recipientNames.length === 0) {
+      const sheet = workbook.addWorksheet(t('invoicesReport.sheetNameFallback'));
+      sheet.addRow([t('invoicesReport.noRecipients', {month: this.getMonthLabel()})]);
+      return;
+    }
+
+    const monthLabel = this.getMonthLabel();
+    const usedSheetNames: string[] = [];
+
+    recipientNames.forEach(recipientName => {
+      const sheetName = sanitizeSheetName(recipientName, usedSheetNames);
+      usedSheetNames.push(sheetName);
+
+      const sheet = workbook.addWorksheet(sheetName);
+
+      const titleRow = sheet.addRow([`${recipientName} (${monthLabel})`]);
+      titleRow.getCell(1).font = {bold: true, size: 14};
+
+      this.addLandingFeesTable(sheet, arrivalRecipients[recipientName]);
+      this.addCustomsFeesTable(sheet, customsRecipients[recipientName], false);
+      this.addCustomsFeesTable(sheet, customsRecipients[recipientName], true);
+    });
+  }
+
+  landingFeeColumns(): Column[] {
+    return [
+      {header: t('invoicesReport.colDate'), width: 12, numFmt: DATE_FORMAT},
+      {header: t('invoicesReport.colTime'), width: 8},
+      {header: t('invoicesReport.colImmatriculation'), width: 15},
+      {header: 'MTOW', width: 8},
+      {header: t('invoicesReport.colFirstname'), width: 16},
+      {header: t('invoicesReport.colLastname'), width: 16},
+      {header: t('invoicesReport.colEmail'), width: 30},
+      {header: t('invoicesReport.colFlightType'), width: 18},
+      {header: t('invoicesReport.colSubtotal'), width: 12, numFmt: MONEY_FORMAT, total: true},
+      {header: t('invoicesReport.colVat'), width: 12, numFmt: MONEY_FORMAT, total: true},
+      {header: t('invoicesReport.colRounding'), width: 12, numFmt: MONEY_FORMAT, total: true},
+      {header: t('invoicesReport.colTotal'), width: 12, numFmt: MONEY_FORMAT, total: true},
+    ];
+  }
+
+  customsFeeColumns(): Column[] {
+    return [
+      {header: t('invoicesReport.colDate'), width: 12, numFmt: DATE_FORMAT},
+      {header: t('invoicesReport.colImmatriculation'), width: 15},
+      {header: t('invoicesReport.colEmail'), width: 30},
+      {header: t('invoicesReport.colDirection'), width: 18},
+      {header: t('invoicesReport.colSubtotal'), width: 12, numFmt: MONEY_FORMAT, total: true},
+      {header: t('invoicesReport.colVat'), width: 12, numFmt: MONEY_FORMAT, total: true},
+      {header: t('invoicesReport.colRounding'), width: 12, numFmt: MONEY_FORMAT, total: true},
+      {header: t('invoicesReport.colTotal'), width: 12, numFmt: MONEY_FORMAT, total: true},
+    ];
+  }
+
+  addLandingFeesTable(sheet, arrivals) {
+    if (!arrivals || arrivals.length === 0) {
+      return;
+    }
+
+    const totals = [0, 0, 0, 0];
+
+    const rows = arrivals.map(arrival => {
+      const {
+        date,
+        time,
+        immatriculation,
+        mtow,
+        firstname,
+        lastname,
+        email,
+        flightType,
+        feeTotalNet,
+        feeVat,
+        feeRoundingDifference,
+        feeTotalGross,
+        landingFeeTotal // fallback only for the "transition" month
+      } = arrival;
+
+      const amounts = typeof feeTotalGross === 'number'
+        ? [
+          toAmount(feeTotalNet),
+          toAmount(feeVat),
+          toAmount(feeRoundingDifference),
+          toAmount(feeTotalGross)
+        ]
+        // fallback only for the "transition" month
+        : [null, null, null, toAmount(landingFeeTotal)];
+
+      addAmounts(totals, amounts);
+
+      return [
+        toDateValue(date),
+        dates.formatTime(date, time),
+        immatriculation,
+        mtow,
+        firstname,
+        lastname,
+        email,
+        getFlightTypeLabel(flightType),
+        ...amounts
+      ];
+    });
+
+    this.addTable(sheet, t('invoicesReport.landingFees'), this.landingFeeColumns(), rows, totals);
+  }
+
+  addCustomsFeesTable(sheet, customsDeclarations, cancelled) {
+    const relevantDeclarations = customsDeclarations ? customsDeclarations
+      .filter(declaration => cancelled ? declaration.cancelled === true : declaration.cancelled !== true)
+      : [];
+
+    if (relevantDeclarations.length === 0) {
+      return;
+    }
+
+    const totals = [0, 0, 0, 0];
+
+    const rows = relevantDeclarations.map(declaration => {
+      const {date, direction, registration, email, fee} = declaration;
+
+      const amounts = typeof fee === 'number'
+        // fallback only for the "transition" month
+        ? [null, null, null, toAmount(fee)]
+        : [
+          toAmount(fee && fee.totalNet),
+          toAmount(fee && fee.vat),
+          toAmount(fee && fee.roundingDifference),
+          toAmount(fee && fee.totalGrossRounded)
+        ];
+
+      addAmounts(totals, amounts);
+
+      return [
+        toDateValue(date),
+        registration,
+        email,
+        direction === 'arrival'
+          ? t('invoicesReport.directionArrival')
+          : t('invoicesReport.directionDeparture'),
+        ...amounts
+      ];
+    });
+
+    const subHeader = cancelled
+      ? t('invoicesReport.customsFeesCancelled')
+      : t('invoicesReport.customsFees');
+
+    this.addTable(sheet, subHeader, this.customsFeeColumns(), rows, totals);
+  }
+
+  /**
+   * Append a titled table to a sheet: a subheader, a bold header row, the data
+   * rows, and a totals row of SUM formulas over just this table's rows.
+   *
+   * @param totals the JS sums, in order of the columns flagged `total`. They are
+   *   written as each formula's cached result.
+   */
+  addTable(sheet, subHeader: string, columns: Column[], rows: any[][], totals: number[]) {
+    sheet.addRow([]);
+
+    const subHeaderRow = sheet.addRow([subHeader]);
+    subHeaderRow.getCell(1).font = {bold: true, size: 12};
+
+    const headerRow = sheet.addRow(columns.map(column => column.header));
+    headerRow.font = {bold: true};
+
+    const firstDataRowNumber = headerRow.number + 1;
+
+    rows.forEach(values => {
+      const row = sheet.addRow(values);
+      columns.forEach((column, index) => {
+        if (column.numFmt) {
+          row.getCell(index + 1).numFmt = column.numFmt;
+        }
+      });
+    });
+
+    const lastDataRowNumber = firstDataRowNumber + rows.length - 1;
+
+    const totalsRow = sheet.addRow([]);
+    let totalIndex = 0;
+    columns.forEach((column, index) => {
+      if (!column.total) {
+        return;
+      }
+      const letter = columnLetter(index + 1);
+      const cell = totalsRow.getCell(index + 1);
+      // The cached result keeps the total readable by tools that do not
+      // evaluate formulas; without it they see an empty cell.
+      cell.value = {
+        formula: `SUM(${letter}${firstDataRowNumber}:${letter}${lastDataRowNumber})`,
+        result: totals[totalIndex]
+      };
+      cell.numFmt = column.numFmt;
+      cell.font = {bold: true};
+      totalIndex++;
+    });
+
+    columns.forEach((column, index) => {
+      const sheetColumn = sheet.getColumn(index + 1);
+      if (!sheetColumn.width || sheetColumn.width < column.width) {
+        sheetColumn.width = column.width;
+      }
+    });
+  }
+}
+
+export default InvoicesExcelReport;
diff --git a/src/util/InvoicesReport.ts b/src/util/InvoicesReport.ts
index 840a240f..e3c7a4d4 100644
--- a/src/util/InvoicesReport.ts
+++ b/src/util/InvoicesReport.ts
@@ -1,6 +1,4 @@
-import firebase, {getIdToken} from './firebase';
-import {get, query, orderByChild, startAt, endAt} from 'firebase/database';
-import {firebaseToLocal} from './movements';
+import InvoicesReportData from './InvoicesReportData';
 import dates from '../util/dates';
 import {getLabel as getFlightTypeLabel} from '../util/flightTypes';
 import formatMoney from './formatMoney'
@@ -8,45 +6,12 @@ import i18n from '../i18n';
 
 const t = i18n.getFixedT('de');
 
-import moment from 'moment';
-
 import pdfMake from 'pdfmake/build/pdfmake';
 import pdfFonts from 'pdfmake/build/vfs_fonts';
 
 (window as any).pdfFonts = pdfFonts; // actually not necessary, but otherwise `pdfFonts` is unused and would be removed
 
-class InvoicesReport {
-
-  get checkoutRecipientName() {
-    return t('invoicesReport.onlinePayments');
-  }
-
-  get cashRecipientName() {
-    return t('invoicesReport.cashPayments');
-  }
-
-
-  year: number;
-  month: number;
-  startDate: string;
-  endDate: string;
-  creationDate: any;
-  options: any;
-
-  constructor(year, month, options = {}) {
-    const monthStr = (month < 10 ? '0' : '') + month
-    const day = '01';
-
-    this.year = year
-    this.month = month
-
-    this.startDate = year + '-' + monthStr + '-' + day;
-    this.endDate = moment(this.startDate).endOf('month').format('YYYY-MM-DD');
-
-    this.creationDate = moment();
-
-    this.options = options;
-  }
+class InvoicesReport extends InvoicesReportData {
 
   generate(callback) {
     Promise.all([
@@ -58,40 +23,6 @@ class InvoicesReport {
     });
   }
 
-  readArrivals() {
-    return get(query(
-      firebase('/arrivals'),
-      orderByChild('dateTime'),
-      startAt(dates.isoStartOfDay(this.startDate)),
-      endAt(dates.isoEndOfDay(this.endDate))
-    ));
-  }
-
-  async fetchCustomsData(endpoint) {
-    const idToken = await getIdToken()
-    const url = `https://europe-west1-${__FIREBASE_PROJECT_ID__}.cloudfunctions.net/api/customs/${endpoint}?year=${this.year}&month=${this.month}`
-    const response = await fetch(url, {
-      headers: {
-        'Authorization': `Bearer ${idToken}`
-      }
-    })
-
-    if (!response.ok) {
-      console.log(`Failed to fetch customs ${endpoint}`, response)
-      throw new Error(`Failed to fetch customs ${endpoint}`)
-    }
-
-    return await response.json()
-  }
-
-  async readCustomsDeclarationsInvoices() {
-    return this.fetchCustomsData('invoices')
-  }
-
-  async readCustomsDeclarationsCheckouts() {
-    return this.fetchCustomsData('checkouts')
-  }
-
   build(arrivals, customsInvoices, customsCheckouts, callback) {
     const content = this.buildContent(arrivals, customsInvoices, customsCheckouts)
     const docDefinition = {
@@ -112,27 +43,8 @@ class InvoicesReport {
   }
 
   buildContent(arrivals, customsInvoices, customsCheckouts) {
-    const filteredArrivals = this.filterArrivals(arrivals)
-    const arrivalRecipients = this.groupArrivalsByRecipient(filteredArrivals)
-    const customsRecipients = this.groupCustomsDeclarationsByRecipient(customsInvoices)
-
-    customsRecipients[this.checkoutRecipientName] = customsCheckouts
-
-    let recipientNames = Array.from(new Set([
-      ...Object.keys(arrivalRecipients),
-      ...Object.keys(customsRecipients)
-    ]))
-
-    // sort names; checkoutRecipientName always first, cashRecipientName second (when present)
-    const hasCash = arrivalRecipients[this.cashRecipientName] !== undefined
-    recipientNames = recipientNames.filter(
-      name => name !== this.checkoutRecipientName && name !== this.cashRecipientName
-    )
-    recipientNames.sort()
-    if (hasCash) {
-      recipientNames.unshift(this.cashRecipientName)
-    }
-    recipientNames.unshift(this.checkoutRecipientName)
+    const {arrivalRecipients, customsRecipients, recipientNames} =
+      this.groupAll(arrivals, customsInvoices, customsCheckouts)
 
     const monthLabel = this.getMonthLabel()
 
@@ -158,70 +70,6 @@ class InvoicesReport {
     return content
   }
 
-  filterArrivals(arrivals) {
-    const filtered: any[] = []
-
-    arrivals.forEach(record => {
-      const arrival = firebaseToLocal(record.val());
-      if (arrival.paymentMethod && arrival.paymentMethod.status !== 'pending') {
-        filtered.push(arrival)
-      }
-    });
-
-    return filtered
-  }
-
-  groupArrivalsByRecipient(arrivals) {
-    // Null-prototype: invoiceRecipientName is user-controlled, so a value like
-    // '__proto__' or 'constructor' must be an ordinary key, not touch the
-    // prototype chain (which would corrupt grouping / crash the report).
-    const recipients = Object.create(null)
-
-    arrivals.forEach(arrival => {
-      const invoiceRecipientName = arrival.paymentMethod.method === 'invoice'
-        ? arrival.paymentMethod.invoiceRecipientName
-        : arrival.paymentMethod.method === 'checkout'
-          ? this.checkoutRecipientName
-          : arrival.paymentMethod.method === 'cash'
-            ? this.cashRecipientName
-            : undefined
-
-      if (invoiceRecipientName) {
-        if (!recipients[invoiceRecipientName]) {
-          recipients[invoiceRecipientName] = []
-        }
-
-        recipients[invoiceRecipientName].push(arrival)
-      }
-    });
-
-    return recipients
-  }
-
-  groupCustomsDeclarationsByRecipient(customsDeclarations) {
-    // Null-prototype: invoiceRecipientName is user-controlled, so a value like
-    // '__proto__' or 'constructor' must be an ordinary key, not touch the
-    // prototype chain (which would corrupt grouping / crash the report).
-    const recipients = Object.create(null)
-
-    customsDeclarations.forEach(customsDeclaration => {
-      const invoiceRecipientName = customsDeclaration.invoiceRecipientName
-
-      if (!recipients[invoiceRecipientName]) {
-        recipients[invoiceRecipientName] = []
-      }
-
-      recipients[invoiceRecipientName].push(customsDeclaration)
-    });
-
-    return recipients
-  }
-
-  getMonthLabel() {
-    const monthName = t(`months.${this.month - 1}`)
-    return `${monthName} ${this.year}`
-  }
-
   addLandingFeesTable(recipientName, arrivals, content) {
     if (!arrivals || arrivals.length === 0) {
       return
diff --git a/src/util/InvoicesReportData.spec.ts b/src/util/InvoicesReportData.spec.ts
new file mode 100644
index 00000000..8326a875
--- /dev/null
+++ b/src/util/InvoicesReportData.spec.ts
@@ -0,0 +1,107 @@
+describe('util', () => {
+  describe('InvoicesReportData', () => {
+    let InvoicesReportData;
+    let get;
+
+    beforeEach(() => {
+      global.__CONF__ = {
+        aerodrome: {
+          ICAO: 'LSZT',
+          runways: [{name: '10', type: 'A'}, {name: '28', type: 'A'}],
+        },
+        enabledFlightTypes: {0: 'private', 1: 'instruction'},
+        memberManagement: false,
+      };
+
+      jest.resetModules();
+      jest.mock('./firebase');
+      jest.mock('firebase/database', () => ({
+        get: jest.fn(),
+        query: jest.fn(ref => ref),
+        orderByChild: jest.fn(),
+        startAt: jest.fn(),
+        endAt: jest.fn(),
+      }));
+
+      get = require('firebase/database').get;
+      InvoicesReportData = require('./InvoicesReportData').default;
+    });
+
+    function makeArrivalsSnapshot(arrivals) {
+      const records = arrivals.map(arrival => ({
+        val: () => ({
+          dateTime: new Date(`${arrival.date}T${arrival.time}:00`).toISOString(),
+          immatriculation: 'HB-KOF',
+          paymentMethod: arrival.paymentMethod,
+        }),
+      }));
+      return {forEach: fn => records.forEach(fn)};
+    }
+
+    // collect() is the wiring InvoicesExcelReport.generate() actually calls in
+    // production: readArrivals + the two customs endpoints, fed into groupAll.
+    // Nothing else exercises it end to end.
+    describe('collect', () => {
+      it('fetches arrivals and customs data and groups them by recipient', async () => {
+        get.mockResolvedValue(makeArrivalsSnapshot([
+          {
+            date: '2023-06-01', time: '10:00',
+            paymentMethod: {method: 'invoice', status: 'paid', invoiceRecipientName: 'Company A'},
+          },
+          {
+            date: '2023-06-02', time: '11:00',
+            paymentMethod: {method: 'checkout', status: 'paid'},
+          },
+        ]));
+
+        const report = new InvoicesReportData(2023, 6);
+        report.readCustomsDeclarationsInvoices = jest.fn().mockResolvedValue([
+          {invoiceRecipientName: 'Company A', date: '2023-06-01', fee: 10},
+        ]);
+        report.readCustomsDeclarationsCheckouts = jest.fn().mockResolvedValue([
+          {date: '2023-06-03', fee: 5},
+        ]);
+
+        const {recipientNames, arrivalRecipients, customsRecipients} = await report.collect();
+
+        expect(recipientNames).toEqual(['Online-Zahlungen', 'Company A']);
+        expect(arrivalRecipients['Company A']).toHaveLength(1);
+        expect(customsRecipients['Company A']).toHaveLength(1);
+        // The checkout customs declarations are filed under the same recipient
+        // name as checkout arrivals.
+        expect(customsRecipients['Online-Zahlungen']).toHaveLength(1);
+      });
+
+      it('excludes pending arrivals, matching the PDF report', async () => {
+        get.mockResolvedValue(makeArrivalsSnapshot([
+          {
+            date: '2023-06-01', time: '10:00',
+            paymentMethod: {method: 'invoice', status: 'pending', invoiceRecipientName: 'Company A'},
+          },
+        ]));
+
+        const report = new InvoicesReportData(2023, 6);
+        report.readCustomsDeclarationsInvoices = jest.fn().mockResolvedValue([]);
+        report.readCustomsDeclarationsCheckouts = jest.fn().mockResolvedValue([]);
+
+        const {recipientNames, arrivalRecipients} = await report.collect();
+
+        // The checkout recipient placeholder is always present (it carries the
+        // customs checkouts group even when there are none); the pending
+        // arrival's recipient must not be.
+        expect(recipientNames).toEqual(['Online-Zahlungen']);
+        expect(arrivalRecipients['Company A']).toBeUndefined();
+      });
+
+      it('rejects when a customs endpoint fails', async () => {
+        get.mockResolvedValue(makeArrivalsSnapshot([]));
+
+        const report = new InvoicesReportData(2023, 6);
+        report.readCustomsDeclarationsInvoices = jest.fn().mockRejectedValue(new Error('down'));
+        report.readCustomsDeclarationsCheckouts = jest.fn().mockResolvedValue([]);
+
+        await expect(report.collect()).rejects.toThrow('down');
+      });
+    });
+  });
+});
diff --git a/src/util/InvoicesReportData.ts b/src/util/InvoicesReportData.ts
new file mode 100644
index 00000000..80718ee3
--- /dev/null
+++ b/src/util/InvoicesReportData.ts
@@ -0,0 +1,199 @@
+import firebase, {getIdToken} from './firebase';
+import {get, query, orderByChild, startAt, endAt} from 'firebase/database';
+import {firebaseToLocal} from './movements';
+import dates from '../util/dates';
+import i18n from '../i18n';
+
+const t = i18n.getFixedT('de');
+
+import moment from 'moment';
+
+/**
+ * Everything the invoice recipient reports need before rendering: fetching the
+ * arrivals and customs declarations for a month, and grouping them by invoice
+ * recipient. Rendering is left to the subclasses (PDF / Excel), so both formats
+ * are guaranteed to show the same data in the same order.
+ */
+class InvoicesReportData {
+
+  get checkoutRecipientName() {
+    return t('invoicesReport.onlinePayments');
+  }
+
+  get cashRecipientName() {
+    return t('invoicesReport.cashPayments');
+  }
+
+  year: number;
+  month: number;
+  startDate: string;
+  endDate: string;
+  creationDate: any;
+  options: any;
+
+  constructor(year, month, options = {}) {
+    const monthStr = (month < 10 ? '0' : '') + month
+    const day = '01';
+
+    this.year = year
+    this.month = month
+
+    this.startDate = year + '-' + monthStr + '-' + day;
+    this.endDate = moment(this.startDate).endOf('month').format('YYYY-MM-DD');
+
+    this.creationDate = moment();
+
+    this.options = options;
+  }
+
+  /**
+   * Fetch the month's data and group it by invoice recipient.
+   */
+  collect() {
+    return Promise.all([
+      this.readArrivals(),
+      this.readCustomsDeclarationsInvoices(),
+      this.readCustomsDeclarationsCheckouts()
+    ]).then(([arrivalsResult, customsInvoices, customsCheckouts]) =>
+      this.groupAll(arrivalsResult, customsInvoices, customsCheckouts))
+  }
+
+  /**
+   * Group already fetched data by invoice recipient, in display order.
+   */
+  groupAll(arrivals, customsInvoices, customsCheckouts) {
+    const arrivalRecipients = this.groupArrivalsByRecipient(this.filterArrivals(arrivals))
+    const customsRecipients = this.groupCustomsDeclarationsByRecipient(customsInvoices)
+
+    customsRecipients[this.checkoutRecipientName] = customsCheckouts
+
+    return {
+      arrivalRecipients,
+      customsRecipients,
+      recipientNames: this.getRecipientNames(arrivalRecipients, customsRecipients)
+    }
+  }
+
+  readArrivals() {
+    return get(query(
+      firebase('/arrivals'),
+      orderByChild('dateTime'),
+      startAt(dates.isoStartOfDay(this.startDate)),
+      endAt(dates.isoEndOfDay(this.endDate))
+    ));
+  }
+
+  async fetchCustomsData(endpoint) {
+    const idToken = await getIdToken()
+    const url = `https://europe-west1-${__FIREBASE_PROJECT_ID__}.cloudfunctions.net/api/customs/${endpoint}?year=${this.year}&month=${this.month}`
+    const response = await fetch(url, {
+      headers: {
+        'Authorization': `Bearer ${idToken}`
+      }
+    })
+
+    if (!response.ok) {
+      console.log(`Failed to fetch customs ${endpoint}`, response)
+      throw new Error(`Failed to fetch customs ${endpoint}`)
+    }
+
+    return await response.json()
+  }
+
+  async readCustomsDeclarationsInvoices() {
+    return this.fetchCustomsData('invoices')
+  }
+
+  async readCustomsDeclarationsCheckouts() {
+    return this.fetchCustomsData('checkouts')
+  }
+
+  filterArrivals(arrivals) {
+    const filtered: any[] = []
+
+    arrivals.forEach(record => {
+      const arrival = firebaseToLocal(record.val());
+      if (arrival.paymentMethod && arrival.paymentMethod.status !== 'pending') {
+        filtered.push(arrival)
+      }
+    });
+
+    return filtered
+  }
+
+  groupArrivalsByRecipient(arrivals) {
+    // Null-prototype: invoiceRecipientName is user-controlled, so a value like
+    // '__proto__' or 'constructor' must be an ordinary key, not touch the
+    // prototype chain (which would corrupt grouping / crash the report).
+    const recipients = Object.create(null)
+
+    arrivals.forEach(arrival => {
+      const invoiceRecipientName = arrival.paymentMethod.method === 'invoice'
+        ? arrival.paymentMethod.invoiceRecipientName
+        : arrival.paymentMethod.method === 'checkout'
+          ? this.checkoutRecipientName
+          : arrival.paymentMethod.method === 'cash'
+            ? this.cashRecipientName
+            : undefined
+
+      if (invoiceRecipientName) {
+        if (!recipients[invoiceRecipientName]) {
+          recipients[invoiceRecipientName] = []
+        }
+
+        recipients[invoiceRecipientName].push(arrival)
+      }
+    });
+
+    return recipients
+  }
+
+  groupCustomsDeclarationsByRecipient(customsDeclarations) {
+    // Null-prototype: invoiceRecipientName is user-controlled, so a value like
+    // '__proto__' or 'constructor' must be an ordinary key, not touch the
+    // prototype chain (which would corrupt grouping / crash the report).
+    const recipients = Object.create(null)
+
+    customsDeclarations.forEach(customsDeclaration => {
+      const invoiceRecipientName = customsDeclaration.invoiceRecipientName
+
+      if (!recipients[invoiceRecipientName]) {
+        recipients[invoiceRecipientName] = []
+      }
+
+      recipients[invoiceRecipientName].push(customsDeclaration)
+    });
+
+    return recipients
+  }
+
+  /**
+   * Recipient names in display order: online payments first, cash payments
+   * second (when present), everything else alphabetically.
+   */
+  getRecipientNames(arrivalRecipients, customsRecipients) {
+    let recipientNames = Array.from(new Set([
+      ...Object.keys(arrivalRecipients),
+      ...Object.keys(customsRecipients)
+    ]))
+
+    const hasCash = arrivalRecipients[this.cashRecipientName] !== undefined
+    recipientNames = recipientNames.filter(
+      name => name !== this.checkoutRecipientName && name !== this.cashRecipientName
+    )
+    recipientNames.sort()
+    if (hasCash) {
+      recipientNames.unshift(this.cashRecipientName)
+    }
+    recipientNames.unshift(this.checkoutRecipientName)
+
+    return recipientNames
+  }
+
+  getMonthLabel() {
+    const monthName = t(`months.${this.month - 1}`)
+    return `${monthName} ${this.year}`
+  }
+}
+
+export default InvoicesReportData;
diff --git a/src/util/downloadBlob.spec.ts b/src/util/downloadBlob.spec.ts
new file mode 100644
index 00000000..8ce3a8a7
--- /dev/null
+++ b/src/util/downloadBlob.spec.ts
@@ -0,0 +1,58 @@
+import downloadBlob from './downloadBlob';
+
+describe('util', () => {
+  describe('downloadBlob', () => {
+    let createObjectURL;
+    let revokeObjectURL;
+
+    beforeEach(() => {
+      createObjectURL = jest.fn(() => 'blob:fake-url');
+      revokeObjectURL = jest.fn();
+      (URL as any).createObjectURL = createObjectURL;
+      (URL as any).revokeObjectURL = revokeObjectURL;
+    });
+
+    it('clicks a download link pointing at the blob', () => {
+      const clicks: any[] = [];
+      const originalCreateElement = document.createElement.bind(document);
+      jest.spyOn(document, 'createElement').mockImplementation(tagName => {
+        const element = originalCreateElement(tagName);
+        if (tagName === 'a') {
+          element.click = () => clicks.push({
+            href: element.getAttribute('href'),
+            download: element.getAttribute('download'),
+          });
+        }
+        return element;
+      });
+
+      const blob = new Blob(['x']);
+      downloadBlob('report.xlsx', blob);
+
+      expect(createObjectURL).toHaveBeenCalledWith(blob);
+      expect(clicks).toEqual([{href: 'blob:fake-url', download: 'report.xlsx'}]);
+
+      (document.createElement as any).mockRestore();
+    });
+
+    it('removes the link from the document', () => {
+      downloadBlob('report.xlsx', new Blob(['x']));
+      expect(document.querySelectorAll('a')).toHaveLength(0);
+    });
+
+    it('revokes the object url only after the click has been processed', () => {
+      jest.useFakeTimers();
+      try {
+        downloadBlob('report.xlsx', new Blob(['x']));
+        // Revoking synchronously can cancel a download the browser has only
+        // queued, so it must not have happened yet.
+        expect(revokeObjectURL).not.toHaveBeenCalled();
+
+        jest.runAllTimers();
+        expect(revokeObjectURL).toHaveBeenCalledWith('blob:fake-url');
+      } finally {
+        jest.useRealTimers();
+      }
+    });
+  });
+});
diff --git a/src/util/downloadBlob.ts b/src/util/downloadBlob.ts
new file mode 100644
index 00000000..ba73244d
--- /dev/null
+++ b/src/util/downloadBlob.ts
@@ -0,0 +1,21 @@
+/**
+ * Trigger a browser download for an in-memory blob (used for the generated
+ * Excel workbooks, which are too large to inline as a data URI).
+ */
+const downloadBlob = (filename: string, blob: Blob) => {
+  const url = URL.createObjectURL(blob);
+
+  const link = document.createElement('a');
+  link.setAttribute('href', url);
+  link.setAttribute('download', filename);
+
+  document.body.appendChild(link);
+  link.click();
+  document.body.removeChild(link);
+
+  // Some browsers start the download asynchronously, so revoking in this tick
+  // can cancel it before it begins.
+  setTimeout(() => URL.revokeObjectURL(url), 0);
+};
+
+export default downloadBlob;
diff --git a/src/util/loadExcelJs.spec.ts b/src/util/loadExcelJs.spec.ts
new file mode 100644
index 00000000..564016ee
--- /dev/null
+++ b/src/util/loadExcelJs.spec.ts
@@ -0,0 +1,32 @@
+describe('util', () => {
+  describe('loadExcelJs', () => {
+    describe('resolveWorkbookConstructor', () => {
+      let resolveWorkbookConstructor;
+
+      beforeEach(() => {
+        resolveWorkbookConstructor = require('./loadExcelJs').resolveWorkbookConstructor;
+      });
+
+      it('uses Workbook when it is exposed directly on the namespace', () => {
+        class FakeWorkbook {}
+        const result = resolveWorkbookConstructor({Workbook: FakeWorkbook, default: {}});
+        expect(result).toBe(FakeWorkbook);
+      });
+
+      it('falls back to default.Workbook, as a raw ESM dynamic import exposes it', () => {
+        class FakeWorkbook {}
+        const result = resolveWorkbookConstructor({default: {Workbook: FakeWorkbook}});
+        expect(result).toBe(FakeWorkbook);
+      });
+    });
+
+    describe('default export', () => {
+      it('resolves with the Workbook constructor from a real dynamic import', async () => {
+        const loadWorkbookConstructor = require('./loadExcelJs').default;
+        const Workbook = await loadWorkbookConstructor();
+        expect(typeof Workbook).toBe('function');
+        expect(new Workbook()).toBeInstanceOf(Workbook);
+      });
+    });
+  });
+});
diff --git a/src/util/loadExcelJs.ts b/src/util/loadExcelJs.ts
new file mode 100644
index 00000000..d635a63e
--- /dev/null
+++ b/src/util/loadExcelJs.ts
@@ -0,0 +1,24 @@
+/**
+ * exceljs weighs about a megabyte, so it is loaded on demand. Keeping the
+ * dynamic import in its own module lets webpack split it into a separate chunk
+ * that is only fetched when a report is actually generated, and gives tests a
+ * single seam to stub.
+ */
+
+/**
+ * Under a raw ESM dynamic import, a CJS module like exceljs is only reachable
+ * via `.default`; some bundler/interop combinations instead (or additionally)
+ * expose its named exports directly on the namespace object. Exported as a
+ * pure function so both shapes can be tested deterministically — a mocked
+ * dynamic import goes through Babel's own interop shim, which does not
+ * reliably keep the two shapes distinct.
+ */
+export const resolveWorkbookConstructor = (excelJsModule: any): any =>
+  excelJsModule.Workbook || excelJsModule.default.Workbook;
+
+const loadWorkbookConstructor = async (): Promise<any> => {
+  const excelJs: any = await import('exceljs');
+  return resolveWorkbookConstructor(excelJs);
+};
+
+export default loadWorkbookConstructor;
diff --git a/src/util/report.spec.ts b/src/util/report.spec.ts
new file mode 100644
index 00000000..bcab1255
--- /dev/null
+++ b/src/util/report.spec.ts
@@ -0,0 +1,49 @@
+global.__CONF__ = {
+  aerodrome: {
+    ICAO: 'LSZT',
+    runways: [{name: '10', type: 'A'}, {name: '28', type: 'A'}],
+  },
+  enabledFlightTypes: {0: 'private', 1: 'instruction'},
+  memberManagement: false,
+};
+
+// invoicesExcel is a thin wrapper, but it is the one place that forwards
+// (year, month, options) into the InvoicesExcelReport constructor — nothing
+// else in the suite goes through this file, so an argument-order slip here
+// (e.g. swapping year/month) would otherwise go uncaught.
+jest.mock('./InvoicesExcelReport', () => {
+  const construct = jest.fn();
+  const MockInvoicesExcelReport = jest.fn().mockImplementation(function (this: any, ...args: any[]) {
+    construct(...args);
+    this.generate = jest.fn().mockResolvedValue('the-blob');
+  });
+  (MockInvoicesExcelReport as any).__construct = construct;
+  return {__esModule: true, default: MockInvoicesExcelReport};
+});
+
+describe('util', () => {
+  describe('report', () => {
+    describe('invoicesExcel', () => {
+      it('forwards year, month and options to InvoicesExcelReport and resolves with its result', async () => {
+        const {invoicesExcel} = require('./report');
+        const InvoicesExcelReport = require('./InvoicesExcelReport').default;
+        const options = {format: 'excel'};
+
+        const result = await invoicesExcel(2024, 11, options);
+
+        expect((InvoicesExcelReport as any).__construct).toHaveBeenCalledWith(2024, 11, options);
+        expect(result).toBe('the-blob');
+      });
+
+      it('propagates a rejection instead of swallowing it', async () => {
+        const InvoicesExcelReport = require('./InvoicesExcelReport').default;
+        InvoicesExcelReport.mockImplementationOnce(function (this: any) {
+          this.generate = jest.fn().mockRejectedValue(new Error('failed'));
+        });
+        const {invoicesExcel} = require('./report');
+
+        await expect(invoicesExcel(2024, 11, {})).rejects.toThrow('failed');
+      });
+    });
+  });
+});
diff --git a/src/util/report.ts b/src/util/report.ts
index fa6614c4..ffecd6d6 100644
--- a/src/util/report.ts
+++ b/src/util/report.ts
@@ -2,6 +2,7 @@ import MovementReport from './MovementReport';
 import LandingsReport from './LandingsReport';
 import YearlySummaryReport from './YearlySummaryReport';
 import InvoicesReport from './InvoicesReport'
+import InvoicesExcelReport from './InvoicesExcelReport'
 
 export function airstat(year, month, options) {
   return new Promise(resolve => {
@@ -38,3 +39,9 @@ export function invoices(year, month, options) {
       });
   });
 }
+
+export function invoicesExcel(year, month, options) {
+  // Unlike the callback-based reports above, this one propagates failures so
+  // the caller can stop showing the report as being generated.
+  return new InvoicesExcelReport(year, month, options).generate();
+}
diff --git a/webpack.config.js b/webpack.config.js
index 942873b7..813e3465 100755
--- a/webpack.config.js
+++ b/webpack.config.js
@@ -38,6 +38,9 @@ module.exports = {
   output: {
     path: path.resolve(__dirname, './build'),
     filename: 'bundle.[contenthash].js',
+    // Lazily loaded chunks get their own prefix so the service worker can keep
+    // them out of the precache (see GenerateSW below).
+    chunkFilename: 'chunk.[contenthash].js',
     clean: true,
   },
   resolve: {
@@ -100,7 +103,9 @@ module.exports = {
       new GenerateSW({
         clientsClaim: true,
         skipWaiting: true,
-        exclude: [/\.map$/, /index\.html$/],
+        // Lazily loaded chunks are fetched on demand; precaching them would
+        // make every user download code they may never run.
+        exclude: [/\.map$/, /index\.html$/, /^chunk\./],
         runtimeCaching: [{
           urlPattern: ({request}) => request.mode === 'navigate',
           handler: 'NetworkFirst',