KSEF-FA2
A check of the Polish KSeF FA(3) system – applies to invoices submitted to KSeF; a separate format, not Peppol.
What this error means
KSEF-FA2
This is an FA(2) invoice. Production KSeF rejects FA(2) since 2026-02-01 — only FA(3) is accepted.
How to fix it
Update your invoicing software to generate FA(3) and re-issue the invoice.