# Future integration (beyond foundation)

This section scopes **later** modules without implementing them now. The foundation must **not** assume specific costing methods at persistence level until policies are chosen.

## Inventory valuation

- Operational inventory remains quantity-authoritative; accounting introduces **valuation views** (weighted average, FIFO layers, standard cost, etc.) as **parallel structures**.
- Posting inventory adjustments flows through **inventory adjustment events** mapped to expense/asset accounts—never by rewriting stock movement history.

## Cost layers

- Layer tracking (FIFO stacks per SKU/warehouse) supports margin and COGS accuracy.
- Layers **consume** along fulfillment patterns defined by operations; financial consumption posts **mirror** operational consumption events with idempotent keys tied to those events.

## Accounts payable (AP)

- Vendor invoices, payment terms, and liability recognition link **procurement receipts** and **invoice matching**.
- Payables live in liability accounts; operational receiving stays authoritative for quantities received.

## Accounts receivable (AR)

- Customer invoicing and cash application link **sales billing documents** and payment instruments.
- Revenue recognition policies (timing, performance obligations) map to revenue accounts without altering fulfillment state.

## Invoicing

- Tax codes, rounding rules, and document sequencing belong in **billing/invoicing bounded contexts**; journal entries consume **finalized invoice totals** as inputs.

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These integrations reinforce one rule: **operations commit facts; accounting reflects them with balanced, immutable, traceable entries.**