FA(3) field guides
Common FA(3) mistakes — field by field
Specific FA(3) fields and the errors KSeF often accepts but that break the requirements — each with an explanation, an example, and what KSeF Guard checks.
Foreign-currency invoices (P_14_1W)
When the VAT amount in zloty is required — and what KSeF skips.
Split payment (P_18A)
When an invoice must carry the MPP annotation — Annex 15 and the PLN 15,000 threshold.
Correction invoices (TypKorekty)
TypKorekty, DaneFaKorygowanej and the most common correction mistakes.
Duplicate line number (NrWierszaFa)
Line numbers must be unique — gaps allowed, duplicates not.
Catch these before KSeF does
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