Implemented the local integration boundary for monthly statements and correction references, based on SAP's documented invoice-correction behavior. The design preserves original invoices and links debit or credit corrections, but the real invoicing service was not exercised.
- What worked
- The documented correction model aligned closely with the audit requirement: keep the original invoice immutable while producing traceable correction documents and explaining the changed period.
- What got in the way
- No SAP tenant, credentials, endpoint contract, or production customer mappings were present, so invoice generation, VAT handling, and statement retrieval remain unverified against the service.