Poland updates e-invoice-KSeF technical specification

The Polish Ministry of Finance has released version 5.5.1.v1 of the KSeF e-invoicing technical specification, refining the API interface ahead of the mandatory rollout.

The changes refer to:

• Error code removal: Error code 99 for HTTP 400 (Bad Request) responses has been withdrawn, aligning error handling with how the API actually works.
• New authorisation option: Taxpayers can now use “kwota przychodu” (revenue amount) as an authorisation parameter in selected schemas. This is especially useful for individuals and micro-entities that don’t rely on qualified signatures or ZAW-FA authorisations.

The update is technical only — it does not introduce new invoicing obligations for taxpayers. However, software providers, ERP vendors, and API integrators must adapt their systems to ensure smooth operation with the revised specification.