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Mandatory KSeF takes effect on 1 February 2026! The invoicing revolution is becoming a reality and brings businesses many new obligations. What happens if a business does not implement KSeF on time? We explain in this article.
Mandatory KSeF from 1 February 2026: does it apply to everyone? Implementation and the transition period
KSeF, the National e-Invoicing System, is a system developed by the Ministry of Finance for issuing, sharing and receiving structured invoices.
From 1 February 2026, KSeF will be mandatory for all businesses whose turnover in 2024 exceeded PLN 200 million.
From 1 April 2026, the obligation to issue invoices through KSeF will cover other businesses. The only exception is the smallest businesses whose monthly gross sales do not exceed PLN 10,000. They can use the exemption until the end of 2026.
We are therefore in a transition period, with full implementation for all businesses in Poland scheduled for 1 January 2027. In practice, however, KSeF obligations begin on 1 February this year, and not only for the largest entities.
Penalties for late implementation and KSeF errors: Article 106ni of the VAT Act, effective from 1 January 2027
What are the consequences of failing to implement KSeF on time or comply with its rules? Article 106ni of the VAT Act sets out monetary penalties for three main breaches:
- Failure to issue a structured invoice through KSeF despite an obligation to do so.
- Issuing an invoice that does not follow the prescribed template during a KSeF outage or unavailability, or when issuing a structured invoice is impossible for another reason.
- Failure to submit an invoice to KSeF within the required time limit.
Under Article 106ni(1), these breaches carry a penalty of up to 100% of the VAT shown on an invoice issued outside KSeF, or up to 18.7% of the total amount due if the invoice does not specify VAT.
The head of the tax office imposes the penalty by decision. It must be paid within 14 days of service of that decision.
However, the entire provision enters into force only on 1 January 2027. Businesses that fail to implement KSeF on time therefore do not yet need to fear these administrative penalties in the current year.
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KSeF and Fiscal Penal Code sanctions: criminal fiscal liability for invoicing
Other sanctions for unreliable or incorrect invoicing, including invoicing within KSeF, must not be forgotten. Existing Fiscal Penal Code provisions remain applicable, particularly Article 62, which provides for:
- A fine of up to 180 daily rates for failing to issue an invoice, issuing it incorrectly or refusing to hand it over.
- A fine of up to 180 daily rates for failing to retain an issued or received invoice despite being obliged to do so.
- A fine of up to 180 daily rates for making a sale without recording it on a cash register or failing to issue the cash-register document.
- A fine of up to 720 daily rates, imprisonment for at least one year, or both, for issuing an unreliable invoice, meaning one that does not reflect reality.
- A fine of up to 720 daily rates, imprisonment for at least one year, or both, for using an unreliably issued invoice.
- A fine of up to 720 daily rates, imprisonment, or both, for issuing or using an unreliable invoice with a tax amount of low value.
These Fiscal Penal Code penalties can already be imposed this year, including where a breach indirectly concerns KSeF, for example when an incorrect or unreliable invoice is issued through the new system.
In subsequent years, once Article 106ni takes effect, there will be even more potential penalties for incorrect invoicing.
However, the same act cannot attract two different sanctions: both the administrative penalty under Article 106ni of the VAT Act and the criminal fiscal sanction under Article 62 of the Fiscal Penal Code.
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Summary
KSeF implementation dates and the start of administrative penalties are separate matters. The article explains the phased rollout, the breaches covered by Article 106ni and the Fiscal Penal Code sanctions that already apply to incorrect invoicing. A temporary absence of KSeF administrative penalties does not remove other invoicing responsibilities.
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