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Generate valid FA_VAT (KSeF) invoices, before the mandate catches you unprepared.

Poland's KSeF (Krajowy System e-Faktur) is not a future mandate - it is active now: large taxpayers must issue through it from 1 February 2026, most B2B businesses from 1 April 2026, and micro-enterprises from 1 January 2027. Every invoice becomes a FA_VAT XML document that KSeF, the centralized government clearance platform, assigns an official reference number to - it is not legally valid until KSeF processes it. CrateAPI generates and validates that FA_VAT XML from a plain JSON invoice model: standard invoices at Poland's current VAT rates (23%, 8%, 5%), ready for you to submit through your own KSeF channel.

We generate and validate for free, right now — submitting to KSeF and getting your NrKSeF number stay with you, through your own API token or certificate session. CrateAPI does not submit invoices to KSeF.

Part of CrateAPI's format coverage — see all formats →

How it fits your pipeline

  1. Send a JSON invoice to generate/ksef - you get back FA_VAT XML built on the current schema (FA(2)).
  2. Run it through validate/ksef for XSD-structural validation (free, no key) before you submit.
  3. Submit the XML to KSeF through your own channel - the government platform assigns the official NrKSeF reference number. CrateAPI does not transmit invoices.

Who this is for

  1. Software vendors — adding FA_VAT output to an ERP, invoicing tool or SaaS that bills Polish VAT payers before the 2026 mandate hits.
  2. Accountants and biura rachunkowe — who need an independent structural check before a client's invoice reaches KSeF.
  3. Freelancers and small businesses — who need a compliant FA_VAT XML ahead of the 1 April 2026 B2B deadline, or the 1 January 2027 micro-enterprise deadline.

What you get today

  1. A free validator — no key, no signup: paste XML, get every structural finding.
  2. Standard invoices (type 380) at Poland's current VAT rates - 23% standard, 8% and 5% reduced - derived from a single canonical VAT category field.
  3. Strict scope, honestly enforced: correction invoices (KOR), advance payments (ZAL) and historical VAT rates are rejected with a clear 422, never silently approximated.
CrateAPI does not submit invoices to KSeF and does not issue the official NrKSeF number. The XML we generate is pre-flight - submit it to the KSeF platform through your own channel (API token or certificate-based session) to receive the legally valid reference. Ours is the format layer: make sure the FA_VAT XML is structurally valid before it ever reaches the government platform.

Curious how Poland's KSeF mandate compares to the rest of the EU? Check our EU e-invoicing mandate tracker.

Try the free validatorFree, live right now Launching — join the listPaid API access, opens at launch
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