What is "penalty-free" — and what is not
Start with the terminology, because this is where the confusion lives. The obligation to use KSeF is already in force — from the date that matches your tier. What was deferred is one specific category of administrative penalties for breaching it.
Per the Polish Ministry of Finance, the rules on imposing penalties take effect only on 1 January 2027 and do not apply retroactively. Between 1 February and 31 December 2026, the tax authority will not impose an administrative penalty for failing to meet KSeF obligations.
The Ministry openly frames this as a window where tax administration focuses on education rather than punishment. That relief is real. But it covers only one thing — the percentage-based monetary penalties under Article 106ni. Everything else stayed exactly where it was.
For context on what arrives in 2027: Article 106ni allows a penalty of up to 100% of the VAT shown on the invoice, or up to 18.7% of the gross amount for invoices that do not separately show VAT. The penalty is issued by the head of the tax office (naczelnik urzędu skarbowego).
Catch one: fiscal-criminal liability does not disappear
Deferring the VAT Act penalties does not suspend the Fiscal Penal Code (Kodeks karny skarbowy, KKS). These are two separate regimes — and during the transition, the second one is live.
Article 62 of the KKS has long provided for a fine for, among other things, failing to issue an invoice, issuing it defectively, or refusing to hand it over. These provisions are not waiting for 2027 — they apply today, independently of KSeF. If an invoice "gets lost" between a PDF and your accountant's inbox during the transition, the absence of a percentage administrative penalty does not mean the matter is closed.
In practice, the tax authority weighs the circumstances — the severity, degree, and frequency of the breach — and can refrain from a penalty in cases of force majeure, such as a genuine system outage. So this is not a "gotcha on your first integration hiccup." But the legal exposure exists, and it is worth knowing rather than assuming 2026 is a consequence-free zone.
Catch two: an invoice outside KSeF is (legally) not an invoice
This is the most practical catch — it hits you regardless of any penalty from the tax office.
Once the obligation applies, an invoice counts as issued only when it has been successfully submitted to KSeF and passed validation, with a UPO (Urzędowe Poświadczenie Odbioru — the official confirmation of receipt) returned to you. A document generated in your software and emailed as a PDF — if it never went through the system — is simply not an invoice under the VAT Act.
The consequence is brutally simple: your buyer cannot deduct VAT from such a document. A switched-on counterparty will reject it and ask for the "KSeF version." Best case, you lose a day to rework. Worse case, the customer holds payment and your cash flow stalls.
A quick example. A Polish JDG (sole proprietorship) issues a March invoice for PLN 12,300 gross (PLN 2,300 VAT) and emails the PDF, reasoning that "there are no penalties until 2027 anyway." The client — a large company already operating in KSeF — sends it back, because its accounting will not accept a document from outside the system. Penalty from the tax office: zero. Real cost: blocked payment and a stressful process fix mid-month.
Catch three: the transition reliefs are a closing window
It is easy to treat 2026 as the end state. That is a mistake — it is scaffolding, and it comes down at year-end.
What specifically expires on 31 December 2026:
The PLN 10,000 threshold for the smallest businesses. Until the end of 2026, the smallest taxpayers may issue invoices outside KSeF, provided the total value of invoiced sales does not exceed PLN 10,000 gross per month. That right is lost starting with the invoice that breaches the limit. From 1 January 2027 the threshold is gone.
Cash-register invoices and simplified invoices. Invoices from fiscal cash registers, and receipts with a NIP (the Polish tax ID) up to PLN 450 treated as simplified invoices, may keep their current form until the end of 2026. After that, every VAT invoice goes through KSeF.
The legacy authorization tokens. The Ministry of Finance is phasing these out in favor of KSeF certificates — a good moment to tidy up how your company authenticates before it becomes compulsory.
And on 1 January 2027 the full Article 106ni penalty regime begins simultaneously. In other words: the day the reliefs expire is the same day the penalties start. There is no overlap period to lean on.
What this means for you today — by segment
Your obligation depends on your tier. The quick reference:
Who KSeF mandatory from Administrative penalties (Art. 106ni) Large taxpayers (VAT sales in 2024 > PLN 200m) 1 February 2026 from 1 January 2027 All other VAT taxpayers (JDG, SMEs, incl. VAT-exempt) 1 April 2026 from 1 January 2027 Smallest firms (invoiced sales ≤ PLN 10,000 gross/month) 1 January 2027 from 1 January 2027
Source: Ministry of Finance schedule for JDG and SMEs.
If you are a large taxpayer, you have been in the system since February, so the transition period is purely a buffer for finishing integrations, not a reason to delay. If you run a JDG or SME, the obligation has applied since April; the penalty-free window is time to learn, not to postpone. If you are one of the smallest firms under PLN 10,000, you formally have until January 2027 — but watch the limit every month: the first invoice that breaches it triggers the obligation immediately.
Checklist: how to use the transition period
Confirm your tier and start date — large (1 Feb), everyone else (1 Apr), smallest (1 Jan 2027, while ≤ PLN 10,000/month).
Start issuing through KSeF now, even if you could technically still stay outside — learning is cheaper when there is no risk attached.
Check that every invoice returns a UPO — that is the proof it was actually issued, not just generated.
Stop emailing PDFs to B2B counterparties — for them, only the KSeF document lets them deduct VAT.
Move to a KSeF certificate rather than waiting for the tokens to be retired.
If you are near the PLN 10,000 threshold, set an alert so you do not miss the invoice that crosses it.
Train your team and accountant on the new flow before penalties begin in January 2027.
Conclusion
"Obligation without penalty" is true — but only in the narrow sense of the percentage administrative penalties under Article 106ni, deferred to 1 January 2027. Fiscal-criminal liability still applies, and an invoice outside KSeF legally does not exist, so your counterparty cannot deduct its VAT. The transition period is not a rules-free zone — it is time to implement calmly before the reliefs expire and the penalties begin. The best way to use it is to start issuing in KSeF today. Try Biurko free for 14 days at biurko.io and move through the transition period without surprises.
FAQ
Are there penalties for KSeF in 2026? Administrative financial penalties under Article 106ni of the VAT Act are not imposed during the transition period, from 1 February to 31 December 2026. However, fiscal-criminal liability under the Fiscal Penal Code for failing to issue or defectively issuing an invoice still applies, independently of KSeF.
When do KSeF penalties start? Full administrative penalties under Article 106ni of the VAT Act take effect on 1 January 2027 and do not apply retroactively. The penalty can reach up to 100% of the VAT on the invoice, or up to 18.7% of the gross amount for invoices without separately shown VAT. It is issued by the head of the tax office.
Can I issue invoices outside KSeF during the transition period? Generally no, if the obligation already applies to you. The exception is the smallest taxpayers with monthly invoiced sales up to PLN 10,000 gross — they may issue outside KSeF until the end of 2026. They lose that right starting with the invoice that breaches the limit.
Is an invoice issued outside KSeF valid? If you are subject to the obligation, an invoice counts as issued only after it is successfully submitted to KSeF and passes validation (with a UPO). A document emailed as a PDF outside the system is not an invoice under the VAT Act, and the buyer cannot deduct its VAT.
Until when are the smallest firms exempt from KSeF? The smallest taxpayers must join KSeF from 1 January 2027, provided the total value of invoiced sales does not exceed PLN 10,000 gross per month. Once the limit is exceeded, the obligation begins immediately — from the invoice that crossed the threshold.