CRATEAPI

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.

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.

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