E-invoicing & validators

KSeF validator

KSeF API 2.6.1, FA(3), current deadlines and limits of pre-validation.

Dynafis checks Polish invoice data against FA(3) and the configured KSeF rule set. The production connector targets KSeF API 2.6.1. Local pre-validation does not replace KSeF acceptance or assignment of an official KSeF number.

Current mandate

KSeF 2.0 is live. Receiving has generally been mandatory since 1 February 2026 and the general issuing obligation has applied since 1 April 2026. The transition for taxpayers with no more than PLN 10,000 of monthly invoiced gross sales ends on 31 December 2026; from 1 January 2027 issuing also applies to this group.

API 2.6.1 and technical warnings

Dynafis targets API 2.6.1, supports rotating public-key selection through publicKeyId and captures the optional X-System-Warning response header. Stricter XML validation effective since 16 July 2026 must be considered before submission.

Before production submission

Verify environment, permission, certificate or token, taxpayer NIP context and FA(3) data. A successful pre-check confirms technical preparation only; KSeF status, KSeF number and UPO provide the authoritative submission evidence.