An invoice integration is a state machine. Its job is to keep business records consistent even when requests are retried or notifications arrive out of order.
01 / Keep credentials server-side
Create the invoice from a trusted backend with narrowly scoped API credentials. Validate the order and amount on that backend instead of trusting values submitted by the browser.
02 / Persist the relationship
Store the invoice identifier with the internal order reference. Choose a retry strategy that does not accidentally create conflicting payment requests. Log operational identifiers without secrets.
03 / Process events defensively
Authenticate callbacks using the provider’s documented scheme. Make event processing idempotent and check allowed state transitions. Do not fulfill an order simply because the customer returned to a success URL.
04 / Reconcile independently
Use a scheduled reconciliation process to identify missing or delayed notifications. Compare authoritative invoice state with your order records and send ambiguous cases for review.
Planning guidance. Confirm procedures against your software version’s documentation and seek qualified support for your environment. Reviewed October 31, 2026.