skills: add accounts-receivable-advanced stub (02-org-100-to-1k)

departments/finance-accounting/02-org-100-to-1k/accounts-receivable-advanced/SKILL.md

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+---
+name: accounts-receivable-advanced
+description: This skill should be used when AR runs as a dedicated standalone invoicing application (not as a sub-module within a books app) — typically a US mid-market company that has outgrown sub-module AR and needs branded invoice templates, recurring billing, structured dunning, dispute management, credit holds, and a formal write-off workflow. The 19-table form of accounts receivable.
+version: 0.1.0
+metadata:
+  author: erphq
+  domain: erpai.studio
+  department: finance-accounting
+  size_tier: 02-org-100-to-1k
+  type: skill
+  scope: internal
+---
+
+# Accounts Receivable — Standalone Invoicing App
+
+> **Status: stub.** This skill exists to unblock build-time `composes:`
+> expansion for [`apps/020-02-fin-invoicing-ar.md`](https://github.com/erphq/appskills/blob/main/apps/020-02-fin-invoicing-ar.md)
+> in [erphq/appskills](https://github.com/erphq/appskills). The deeper
+> Build / Maintain / Scale content needs domain-expert authorship —
+> see TODO markers below. Filed via [erphq/skills#4](https://github.com/erphq/skills/issues/4).
+
+## What This Process Does
+
+`accounts-receivable-advanced` is the **full standalone invoicing-app form** of AR — distinct from the [basic `accounts-receivable` skill at this tier](../accounts-receivable/SKILL.md) which assumes AR is a sub-module within a general-ledger books app.
+
+The differentiator: this is what an organization composes when they need a **dedicated invoicing application** — branded customer-facing invoice templates, recurring billing schedules, formal dunning programs, structured dispute management, collections cases, write-offs, late fees, and a credit-hold workflow. Typical fit: US mid-market company (200–1,000 employees, 500–10k active customers, 500–5k invoices/month) that has outgrown sub-module AR but isn't on a full ERP.
+
+## Materializes as 19 tables
+
+15 entities + 4 line-item children:
+
+| # | Entity | Purpose |
+|---|---|---|
+| 1 | `Customer` (AR-grain) | Credit limit, payment-terms defaults, billing contact |
+| 2 | `InvoiceTemplates` | Branded customer-facing PDF templates |
+| 3 | `Invoices` | The core invoice with status lifecycle (draft → sent → partially-paid → paid → written-off) |
+| 4 | `InvoiceLines` | Line-item children of `Invoices` |
+| 5 | `RecurringInvoiceSchedules` | Subscription / annual-contract auto-billing |
+| 6 | `CreditMemos` | Negative-direction adjustments (returns, billing corrections) |
+| 7 | `CreditMemoLines` | Line-item children of `CreditMemos` |
+| 8 | `PaymentsReceived` | Customer-initiated cash-in |
+| 9 | `PaymentApplications` | Many-to-many mapping of `PaymentsReceived` to `Invoices` |
+| 10 | `BankFeedTransactions` | Inbound bank stream (raw transactions before matching) |
+| 11 | `DunningPolicies` | Cadence + tone config per customer segment |
+| 12 | `DunningEvents` | Generated send-history child of dunning runs |
+| 13 | `Disputes` | Customer-raised dispute records, drives dunning pause |
+| 14 | `WriteOffs` | Formal uncollectible recognition |
+| 15 | `LateFees` | Auto-applied or manual late charges |
+| 16 | `ARAgingSnapshots` | Periodic point-in-time aging captures (for reporting) |
+| 17 | `CollectionsCases` | Long-running collections workstream per dispute / aging trigger |
+| 18 | `CreditHolds` | Block on new orders when credit limit exceeded |
+| 19 | (the 4th line-item child completes the count — see app spec for the exact decomposition) |
+
+(The app spec at [`020-02-fin-invoicing-ar.md`](https://github.com/erphq/appskills/blob/main/apps/020-02-fin-invoicing-ar.md) is the source of truth for the table specs, foreign keys, and column-level recipe.)
+
+## TODO — needs domain-expert authorship
+
+This stub captures the differentiator and the table inventory. The following sections from the standard SKILL.md template still need to be written:
+
+- [ ] **Start Here: ERP•AI Templates** — which template artifacts seed this skill
+- [ ] **Build — Setting It Up** (with Agents / Key Decisions / Common Mistakes)
+- [ ] **Maintain — Keeping It Healthy** (Weekly Rhythm / What to Watch / Exception Handling)
+- [ ] **Scale — Growing It** (Adding Complexity / Automation Opportunities / When You Outgrow This Tier)
+- [ ] **By Industry (at this scale)**
+- [ ] **ERP•AI & Proto** — agent integration patterns
+- [ ] **Related** — cross-links to neighboring skills
+
+Reference: the [neighboring `accounts-receivable` SKILL.md](../accounts-receivable/SKILL.md) at this tier follows the standard structure and is the closest sibling for stylistic reference.
+
+## Related
+
+- [`accounts-receivable`](../accounts-receivable/SKILL.md) — basic AR (this skill's superset replaces sub-module AR)
+- [`general-ledger`](../general-ledger/SKILL.md) — AR posts through the ledger; cash receipts hit AR-clearing
+- [`tax-compliance`](../tax-compliance/SKILL.md) — invoice-line tax computation