Migrating open AR/AP transactions: lessons learned

Closed transactions are the easy part of any AR/AP migration — they're historical record, and once mapped correctly they don't need to behave like anything other than a static number. Open items are different: they need to behave correctly in the target system after go-live, including matching, ageing and payment application.

The most common failure mode is migrating open items as flat balances without their underlying document structure — invoice, credit note, payment, and the links between them. Once that structure is lost, ageing reports and statement runs in the new system produce numbers that don't match what customers and vendors expect.

The fix is to migrate the full document chain, not just the net balance, and to reconcile at document level during every mock cycle — not just at the ledger balance level. It's more work upfront, and it's the difference between a finance team that trusts the new system on day one and one that doesn't.