# Payable Payment Reversal + Cash/Bank Foundation v29

v29 introduces tenant-scoped cash/bank source accounts and controlled supplier-payment reversal.

Cash accounts: cashbox, bank, clearing.

Cash movements are immutable. Supplier-payment reversal restores payable outstanding
balances, appends positive `payment_reversal` entries to the immutable payables ledger,
and, when the payment has a cash account source, creates the opposite positive cash movement.

The original payment and allocations are never deleted.

APIs:
- GET /api/v1/cash/accounts
- POST /api/v1/cash/accounts
- POST /api/v1/payables/payments/{paymentId}/reverse

Permissions:
- cash.account.view
- cash.account.manage
- payables.payment.reverse

For backward compatibility with v28, existing supplier payments may still have no
cash_account_id. v30 will tighten source-account requirements together with cash balance
projection and reconciliation.
