KSeF and the FA(3) schema: a checklist for companies and software vendors

The list below organizes what is worth checking before invoices start flowing to the National e-Invoicing System. The source document is always the official Ministry of Finance documentation, which changes, so confirm deadlines and technical details there.

Schema and data

• An invoice in the current FA(3) schema, validated against the official XSD before sending.
• Correct buyer data (tax ID and name) and a VAT scenario that matches the type of sale.
• Gap-free numbering and invoice uniqueness (the same number and tax ID cannot occur twice).
• Foreign-currency invoices with the NBP rate from the right day and tax converted to zloty.

Authentication and security

• Your own token or certificate with permissions to issue and read invoices, generated in the KSeF application for the company tax ID.
• The token is stored encrypted, never shown again and never written to logs.
• Separate environments (test, DEMO, production) and an explicit environment choice so a trial does not go to production.

Statuses, UPO and errors

• Storing the official acknowledgement of receipt (UPO) with the invoice, together with the KSeF number.
• Retrying the UPO download when it is not ready yet, and an explicit invoice status (draft, sent, accepted, rejected).
• Readable rejection messages: the error code translated into what the user needs to fix.
• Reading the invoice status before resending after an interrupted connection, so a duplicate is not sent.

QR codes and fallback modes

• QR codes on the invoice printout in the modes where they are required.
• Support for offline mode, unavailability and failure with resend deadlines counted in working days.
• A resend queue with reminders and an alert before the deadline.

Corrections and purchase invoices

• Correction invoices with the KSeF number of the original invoice and the correct deadline for settling the VAT reduction.
• Downloading purchase invoices from KSeF and posting them with a person able to approve.