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KSeF 2026 — what you need to do as a business

KSeF came in stages. Most companies already issue their invoices in KSeF, the smallest have until the end of 2026, and from 1 January 2027 a new obligation applies to payments. Here are the deadlines and what to check.

KSeF deadlines

  • 1 February 2026KSeF mandatory for the largest companies (2024 sales above PLN 200 million including VAT). From this day everyone receives invoices through KSeF.
  • 1 April 2026KSeF mandatory for all other companies, except the smallest.
  • until 31 December 2026Companies whose invoiced sales do not exceed PLN 10,000 gross a month may still issue invoices outside KSeF.
  • 1 January 2027KSeF mandatory for everyone. The KSeF number in the title of the transfer paying an invoice (Art. 108g of the Polish VAT Act).
Penalties: under current law, for breaches from 2027 — up to 100% of the VAT on the invoice. The government has adopted a bill that extends the penalty deferral to 31 December 2027 (status as of October 2026). In 2026 the Ministry of Finance imposes no penalties for mistakes in using KSeF.

Who KSeF applies to

The obligation applies to businesses that issue invoices — companies, sole proprietorships and partnerships. The largest companies joined KSeF on 1 February 2026 and the rest on 1 April 2026. Until the end of 2026 the exception is companies with the smallest invoiced sales (up to PLN 10,000 gross a month).

The Ministry of Finance describes the detailed rules and exceptions (in Polish) at ksef.podatki.gov.pl.

What to check now — and before 1 January 2027

  1. Access to KSeF — permissions, a token or a certificate. You manage them in the free KSeF 2.0 Taxpayer Application (Aplikacja Podatnika KSeF 2.0).
  2. Your invoicing software — does it issue invoices in KSeF 2.0 in the FA(3) structure?
  3. Purchase invoices — since 1 February 2026 you receive them through KSeF. Check how they reach your software or your accountant.
  4. Payments from 2027 — a transfer paying a KSeF invoice must include its KSeF number. What this means in practice.
  5. The smallest companies — if you use the PLN 10,000 limit and issue invoices outside KSeF, get ready for 1 January 2027.
  6. Your own system? — test the integration on the KSeF test environment before you send invoices to production.

What to avoid

  • Leaving system changes to the last minute — an ERP integration can take weeks.
  • Ignoring incoming invoices — invoices you don't know about can appear in KSeF.
  • Sending XML in a non-compliant structure — KSeF rejects the invoice and does not assign it a number.
  • Forgetting documents outside KSeF — invoices in KSeF are kept for 10 years, but you archive contracts or payment confirmations yourself.

This English version is a translation of the Polish original, provided for convenience. It describes Polish law, and the Polish version prevails. It is for information only and is not tax advice.

KSeF 2026 — what you need to do as a business | FakturAI