Every KSeF deadline in one table
Date Who it affects What happens 1 September 2025 integrators, software vendors KSeF 1.0 (the old test environment) shut down 1 November 2025 all taxpayers Applications open for the issuer certificate + KSeF 2.0 DEMO environment 1 January 2026 anyone issuing invoices with attachments Prior notification to the Ministry of Finance required (approval up to 30 days) 1 February 2026 large taxpayers (2024 sales > PLN 200M gross) — issuing; everyone — receiving Obligation begins; certificates and offline24 mode go live in production 1 April 2026 all other businesses (except micro firms ≤ PLN 10,000/month) Mandatory invoice issuing in KSeF 1 February – 31 December 2026 everyone covered by the obligation "Protection year" — no administrative fines under Article 106ni 31 December 2026 micro firms ≤ PLN 10,000/month; token users End of the micro-firm deferral; last day tokens are valid 1 January 2027 smallest taxpayers (invoices ≤ PLN 450 / ≤ PLN 10,000 per month) Obligation for everyone; full Article 106ni penalties; tokens withdrawn
1 February 2026 — large companies start, everyone must receive
The first hard date covers two different groups.
Large taxpayers — companies whose 2024 sales including tax exceeded PLN 200 million — must issue invoices through KSeF from this date (source: Biznes.gov.pl).
But there's a second part that's easy to miss: receiving invoices via KSeF became mandatory for all taxpayers on 1 February 2026, regardless of when they themselves start issuing (source: Biznes.gov.pl). If a large supplier sits anywhere in your supply chain, their invoice lands in KSeF from February — and you have to be able to retrieve it there, even as a JDG (sole proprietorship).
This date also brings two operational tools into production: the issuer certificate and offline24 mode, which lets you issue an invoice outside the system and send it in by the next business day at the latest (Article 106nda of the VAT Act). We cover certificates in more detail in our offline24 and issuer certificate guide.
1 April 2026 — mandatory for (almost) everyone
The second wave covers essentially the entire B2B market: small businesses, sole proprietors, companies, and both VAT-registered and VAT-exempt taxpayers. From this date, issuing invoices in KSeF is mandatory for them (source: Biznes.gov.pl).
One exception: the smallest taxpayers, whose total monthly invoice value stays at or below PLN 10,000 gross (with single invoices at or below PLN 450), get a deferral until 1 January 2027. Until then they can keep issuing electronic or paper invoices the old way.
Until 31 December 2026 — the protection year and deferrals
This is where we are right now. Between 1 February and 31 December 2026, no administrative fines under Article 106ni of the VAT Act are applied — the Ministry of Finance calls it a "protection year" to adapt processes and systems (source: ksef.podatki.gov.pl).
Watch out for one trap: the protection covers only KSeF-specific administrative penalties. Fiscal-criminal liability (under the Fiscal Penal Code) for unreliable invoicing or refusing to issue an invoice applies normally throughout 2026.
Two things also end during this period:
the micro-firm deferral (≤ PLN 10,000/month) — December 2026 is the last month without the obligation,
tokens as an authentication method — usable only through 31 December 2026.
1 January 2027 — the grace period ends
Three things happen on the same day:
The smallest taxpayers (invoices ≤ PLN 450 / ≤ PLN 10,000 per month) come under the obligation to issue through KSeF.
Full administrative penalties under Article 106ni (sections 1–3 and 5–7) of the VAT Act take effect. The maximum is up to 100% of the VAT shown on an invoice issued outside KSeF, or up to 18.7% of the total amount due for invoices without VAT.
Tokens are withdrawn. From this date only the issuer certificate and a qualified signature / seal still work.
The legal basis for the whole timeline is the Act of 5 August 2025 (Journal of Laws 2025, item 1203), amending the VAT Act.
Technical dates that are easy to forget
1 November 2025 — applications opened for the issuer certificate (in the KSeF 2.0 Taxpayer Application / certificate module) and the KSeF 2.0 DEMO environment went live. The certificate is free and valid for two years.
1 January 2026 — anyone wanting to issue invoices with attachments in the FA(3) structure must first file a notification with the Ministry of Finance (approval can take up to 30 days).
Consumer invoices (B2C) are outside KSeF — invoices to private individuals not running a business are issued the usual way (paper/PDF) or recorded on a cash register.
Checklist — what to do and when
[ ] Today: confirm your company is already issuing in KSeF (mandatory for most since 1 April 2026).
[ ] Today: make sure you're retrieving purchase invoices from KSeF — mandatory for everyone since 1 February 2026.
[ ] Before the end of 2026: generate an issuer certificate if you're still on a token.
[ ] Before 1 January 2027: drop the token as a login method — it stops working after that date.
[ ] If you're a micro firm ≤ PLN 10,000/month: plan your KSeF entry for 1 January 2027 at the latest.
[ ] All of 2026: treat the protection year as time for testing, not as a pass on accurate invoicing (fiscal-criminal rules still apply).
Summary
The whole calendar boils down to three points: most companies have been issuing in KSeF since April 2026, the penalty-free protection year runs until the end of 2026, and 1 January 2027 simultaneously ends the grace period, retires tokens, and closes the smallest-firm deferral. The rest is detail that a good system handles for you. Biurko tracks certificates, offline24 mode, and submission statuses — and tells you which date actually applies to your company. Create an account and try Biurko free for 14 days.
FAQ
When does KSeF become mandatory? Issuing invoices in KSeF is mandatory from 1 February 2026 for large companies (2024 sales > PLN 200M) and from 1 April 2026 for everyone else. The smallest taxpayers (≤ PLN 10,000/month) join on 1 January 2027. Receiving invoices has been mandatory for all taxpayers since 1 February 2026.
Do small businesses and sole proprietors have to use KSeF? Yes. As a rule the obligation covers all active VAT taxpayers, including sole proprietorships (JDG). The exception is the smallest taxpayers with monthly invoice value up to PLN 10,000 gross — they have a deferral until 1 January 2027, but must still receive invoices from February 2026.
When do KSeF penalties start? Full administrative penalties under Article 106ni of the VAT Act apply from 1 January 2027. 2026 is a penalty-free protection year. The maximum fine is up to 100% of the VAT on an invoice issued outside KSeF (or 18.7% of the gross value for an invoice without VAT).
How long can I keep using KSeF tokens? Tokens work through 31 December 2026. They are withdrawn from 1 January 2027, leaving the issuer certificate and a qualified signature / seal. Tokens don't support offline modes anyway, so it's worth setting up a certificate early.
Do invoices to private individuals (consumers) go to KSeF? No. Invoices to private individuals not running a business are excluded from KSeF. You issue them the usual way — on paper or as a PDF — or record the sale on a cash register.