ERP and accounting integration testing

What ERP and accounting integration testing covers

A sync defect copies itself into the customer's general ledger. An accountant finds it at month-end close or an auditor finds it later, and the product vendor has to explain the difference. We test the connection between a finance product and the ledger it writes to. Ledger math inside accounting software is covered on the accounting software segment page, and payment runs on the AP/AR segment page.

Integration types in scope: cloud accounting REST APIs with OAuth 2.0 apps, ERP web services, flat file journal imports over SFTP, and integration platforms that sit between the product and the ERP.

Sync scenarios per connected system

Each connected system gets its own suite, because two ERPs reject the same bill for different reasons. The suite covers every record type the product writes or reads: vendors, customers, employees, chart of accounts, tax codes, bills, invoices, credit notes, journal entries, payments, and refunds. Each record type runs through create, update, void, and delete, and each run reads the record back from the ERP.

Failure patterns the suite targets:

• Void that never leaves the product. A card transaction is refunded or an expense report is rejected after export, and the ERP keeps the original entry. Expenses stay overstated, and a reimbursement bill left in the ERP can be paid in the next AP run.
• Posting into a closed period. The ERP rejects an entry dated in a locked month. The connector drops the entry, retries it forever, or reposts it with today's date without a record of the change.
• Multi-entity and dimension mapping. An entry posts to the wrong subsidiary or loses its department or cost centre, and the entity's trial balance stops matching the product.

Field mapping and currency conversion

Checks compare every synced field with the agreed mapping.

• Minor units. The ISO 4217 list one, published by SIX on 1 January 2026, gives JPY 0 decimal places and BHD, IQD, JOD, KWD, LYD, OMR, and TND 3 decimal places. A connector that multiplies every amount by 100 posts a 5,000 JPY expense as 500,000 JPY. A connector that keeps two decimals posts a 12.345 KWD card transaction as 12.35 KWD or 12.34 KWD.
• Exchange rate and date. The product can send the functional currency amount, or the ERP can convert at its own rate on the posting date. Checks cover both configurations and the exchange difference account. The FX rate application guide shows the rate and date cases.
• Tax line rounding. Five invoice lines of 0.35 EUR net at 21% VAT give 0.35 EUR of VAT when rounded half up per line, and 0.37 EUR when rounded half up on the 1.75 EUR document total. An ERP that recomputes tax from the tax code rejects the bill or posts the 0.02 EUR difference to a rounding account. The rounding guide lists the rounding modes to test.
• Archived targets. An account, tax code, or vendor archived in the ERP after the mapping was set makes every later entry fail.

Duplicate and missing records

• Duplicate after a timeout. The ERP commits a bill, the response is lost, and the connector creates the bill again. When the ERP pays suppliers, the supplier is paid twice. Tests cut the connection after commit and check that the connector uses an external identifier or looks up the record before it creates one. The idempotency guide shows the request sequences.
• Record skipped by an incremental sync. A sync reads records modified after the last run's timestamp. Records updated in the same second as that timestamp, during pagination, or in another time zone are skipped. Tests write records at those boundaries and count them in both systems.

Error recovery and resync

• Rate limits. RFC 6585 section 4 defines 429 Too Many Requests, and the response MAY include a Retry-After header. Tests check that the connector waits and resumes without skipping a page of records.
• Revoked tokens. Where an accounting system rotates refresh tokens, RFC 9700 section 4.14.2 describes the mechanism: the previous refresh token is invalidated, and when an invalidated token is presented the authorization server revokes the active refresh token. Two sync workers that refresh at the same time can lose the connection. Tests check that the sync stops, alerts the customer, and resumes from the last posted record after reconnection.
• Partial batch failure. One rejected line in a batch of journal entries must not post the rest as an unbalanced entry.
• Resync after a mapping fix. Only failed records post again, and each posts once.

Processing integrity criteria PI1.2 to PI1.5 on the SOC 2 page ask for complete and accurate inputs, processing, and outputs, and these test results are input to that examination.