diff --git a/app/api/invoices/route.ts b/app/api/invoices/route.ts
index ed79f69..4b9fed6 100644
--- a/app/api/invoices/route.ts
+++ b/app/api/invoices/route.ts
@@ -126,9 +126,19 @@ export async function POST(req: Request) {
       status: 'DRAFT',
     };
 
-    const invoice = await prisma.invoice.create({
-      data: invoiceData,
-      include: { client: true },
+    const invoice = await prisma.$transaction(async (tx) => {
+      const seq = await tx.invoiceSequence.upsert({
+        where: { userId: user.id },
+        update: { lastNumber: { increment: 1 } },
+        create: { userId: user.id, lastNumber: 1 },
+      });
+
+      const invoiceNumber = `INV-${String(seq.lastNumber).padStart(3, '0')}`;
+
+      return tx.invoice.create({
+        data: { ...invoiceData, invoiceNumber },
+        include: { client: true },
+      });
     });
 
     return Response.json({ invoice });
diff --git a/app/invoices/page.tsx b/app/invoices/page.tsx
index 46cdc5d..9b60074 100644
--- a/app/invoices/page.tsx
+++ b/app/invoices/page.tsx
@@ -14,6 +14,7 @@ interface Client {
 
 interface Invoice {
   id: string;
+  invoiceNumber?: string | null;
   totalHours: number;
   totalAmount: number;
   createdAt: string;
@@ -42,6 +43,7 @@ interface InvoiceDetailsResponse {
 const buildInvoicePdf = (invoice: Invoice, entries: InvoiceEntry[]) => {
   const doc = new jsPDF();
   const createdAt = new Date(invoice.createdAt).toLocaleDateString();
+  const invoiceNumber = invoice.invoiceNumber || invoice.id;
   const periodStart = invoice.periodStart
     ? new Date(invoice.periodStart).toLocaleDateString()
     : 'N/A';
@@ -49,10 +51,12 @@ const buildInvoicePdf = (invoice: Invoice, entries: InvoiceEntry[]) => {
   const dueDate = invoice.dueDate ? new Date(invoice.dueDate).toLocaleDateString() : 'N/A';
 
   doc.setFontSize(18);
-  doc.text('Worklog Invoice', 14, 20);
+  doc.text('Worklog Invoice', 14, 16);
+  doc.setFontSize(14);
+  doc.text(invoiceNumber, 14, 26);
 
   doc.setFontSize(12);
-  doc.text(`Client: ${invoice.client.name}`, 14, 32);
+  doc.text(`Client: ${invoice.client.name}`, 14, 36);
   doc.text(`Period: ${periodStart} - ${periodEnd}`, 14, 40);
   doc.text(`Due: ${dueDate}`, 14, 48);
   doc.text(`Created: ${createdAt}`, 14, 56);
@@ -164,7 +168,8 @@ export default function InvoicesPage() {
     const details = await fetchInvoiceDetails(invoiceId);
     if (!details) return;
     const doc = buildInvoicePdf(details.invoice, details.entries);
-    doc.save(`invoice-${details.invoice.id}.pdf`);
+    const fileName = `invoice-${details.invoice.invoiceNumber || details.invoice.id}.pdf`;
+    doc.save(fileName);
   };
 
   const handleView = async (invoiceId: string) => {
@@ -310,7 +315,10 @@ export default function InvoicesPage() {
               {invoicesData?.invoices?.length > 0 ? (
                 invoicesData?.invoices?.map((invoice: Invoice) => (
                   <tr key={invoice.id} className="hover:bg-slate-50">
-                    <td className="px-6 py-4 text-slate-900">{invoice.client.name}</td>
+                    <td className="px-6 py-4 text-slate-900">
+                      <div className="font-semibold">{invoice.invoiceNumber || invoice.id}</div>
+                      <div className="text-sm text-slate-600">{invoice.client.name}</div>
+                    </td>
                     <td className="px-6 py-4 text-slate-600">
                       {new Date(invoice.createdAt).toLocaleDateString()}
                     </td>
diff --git a/prisma/migrations/20260402160748_add_invoice_number_and_sequence/migration.sql b/prisma/migrations/20260402160748_add_invoice_number_and_sequence/migration.sql
new file mode 100644
index 0000000..327cd57
--- /dev/null
+++ b/prisma/migrations/20260402160748_add_invoice_number_and_sequence/migration.sql
@@ -0,0 +1,26 @@
+/*
+  Warnings:
+
+  - A unique constraint covering the columns `[userId,invoiceNumber]` on the table `Invoice` will be added. If there are existing duplicate values, this will fail.
+
+*/
+-- AlterTable
+ALTER TABLE "Invoice" ADD COLUMN     "invoiceNumber" TEXT;
+
+-- CreateTable
+CREATE TABLE "InvoiceSequence" (
+    "id" TEXT NOT NULL,
+    "userId" TEXT NOT NULL,
+    "lastNumber" INTEGER NOT NULL DEFAULT 0,
+
+    CONSTRAINT "InvoiceSequence_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE UNIQUE INDEX "InvoiceSequence_userId_key" ON "InvoiceSequence"("userId");
+
+-- CreateIndex
+CREATE UNIQUE INDEX "Invoice_userId_invoiceNumber_key" ON "Invoice"("userId", "invoiceNumber");
+
+-- AddForeignKey
+ALTER TABLE "InvoiceSequence" ADD CONSTRAINT "InvoiceSequence_userId_fkey" FOREIGN KEY ("userId") REFERENCES "User"("id") ON DELETE CASCADE ON UPDATE CASCADE;
diff --git a/prisma/schema.prisma b/prisma/schema.prisma
index 56c152b..247b6ee 100644
--- a/prisma/schema.prisma
+++ b/prisma/schema.prisma
@@ -19,6 +19,7 @@ model User {
   clients     Client[]
   timeEntries TimeEntry[]
   invoices    Invoice[]
+  invoiceSequence InvoiceSequence?
 }
 
 model Client {
@@ -52,6 +53,8 @@ model TimeEntry {
 
 model Invoice {
   id          String    @id @default(cuid())
+  // Human-readable invoice number, e.g. INV-001 (scoped per user)
+  invoiceNumber String?
   totalHours  Float
   totalAmount Float
   // Hourly rate used when the invoice was generated (persisted for historical accuracy)
@@ -70,6 +73,18 @@ model Invoice {
   isPaid      Boolean   @default(false)
   // Optional due date for the invoice; if not provided, default applied in server logic
   dueDate     DateTime?
+
+  @@unique([userId, invoiceNumber])
+}
+
+// Tracks the last invoice sequence number for each user so invoice numbers
+// can auto-increment per user in a concurrency-safe manner.
+model InvoiceSequence {
+  id         String @id @default(cuid())
+  userId     String @unique
+  lastNumber Int    @default(0)
+
+  user User @relation(fields: [userId], references: [id], onDelete: Cascade)
 }
 
 enum InvoiceStatus {