The year 2026 will go down in the history of Polish accounting as the launch of the mandatory National e-Invoicing System (KSeF). The largest taxpayers — with turnover exceeding PLN 200 million in 2024 — have been issuing structured invoices since 1 February 2026, while all other active VAT payers, including small and medium-sized enterprises and sole proprietors, joined the system on 1 April 2026.
Although the revolution has formally taken place, the legislator provided for a transition period that softens its impact. The key date is 31 December 2026 — after that, the rules tighten considerably. The coming months are the right time to put invoicing processes in order.
What applies until the end of 2026?
Under the Act of 5 August 2025, a transition period runs until 31 December 2026, during which:
- No penalties are imposed — tax authorities do not apply administrative sanctions for technical errors, delays in submitting invoices to KSeF, or other lapses related to implementing the system. The head of the National Revenue Administration has confirmed that no penalties will be imposed until the end of 2026.
- The smallest taxpayers may invoice the old way — businesses whose monthly value of sales documented by invoices does not exceed PLN 10,000 gross may issue paper or electronic invoices outside KSeF until the end of 2026. Simplified invoices (receipts with a tax ID up to PLN 450) and cash-register invoices do not count towards the limit.
- Cash-register invoices remain permitted — during the transition period, sales may still be documented with invoices issued via fiscal cash registers.
- The offline24 mode is available to everyone — any taxpayer may issue an invoice outside the system and submit it to KSeF by the next business day, an important safeguard against technical problems.
- No obligation to include the KSeF number in payments — invoice payments do not yet have to include the number identifying the invoice in the system.
What changes from 1 January 2027?
Administrative penalties
From 2027, failing to issue an invoice in KSeF, issuing it in breach of the required schema, or failing to submit an offline-issued invoice on time will carry an administrative penalty — up to 100% of the VAT amount shown on the invoice, or up to 18.7% of the gross value for invoices without VAT. Penalties will be applied proportionately, but the mere risk requires processes to be fully compliant.
KSeF number in payments
From 1 January 2027, transfers for structured invoices between active VAT payers must include the KSeF invoice number (or a collective identifier). The obligation will also cover payments made under the split payment mechanism. This means adapting e-banking systems and accounts payable processes.
The smallest businesses join the system
On 1 January 2027, the exemption for taxpayers within the PLN 10,000 monthly limit expires — all businesses will issue structured invoices, regardless of their scale of operations.
How to prepare your business for 2027?
The final months of the transition period are a good time to:
- verify that all sales invoices reach KSeF correctly and on time, and that offline24 submissions are properly reconciled,
- tidy up KSeF permissions — grant access to employees and your accounting office and generate the certificates required to issue invoices in emergency modes,
- prepare payment processes so that from January 2027 transfers include the KSeF number,
- for the smallest businesses — choose an invoicing tool integrated with KSeF and test it before 1 January 2027.
The LinTax team monitors the KSeF rollout on an ongoing basis and supports clients in adapting their invoicing processes to the new requirements. Feel free to contact us.