KSeF 2026: whether and when you must issue invoices in KSeF

The National e-Invoicing System is the Finance Ministry platform through which invoices between businesses pass. The seller sends the system an XML file in the FA (3) structure. The system checks it, assigns a 35-character KSeF number and makes the invoice available to the buyer. A buyer with a Polish tax ID downloads it directly or through software or an accountant.

Under Article 106na(3) of the VAT Act the invoice is received on the day the number is assigned. Consumers and foreign businesses get it in an agreed way, with a QR code that lets anyone check it in the system without logging in. More on the what KSeF is page, and on the number in the number validator.

The obligation came in stages. The largest businesses, with 2024 sales above PLN 200,000,000 gross, have issued in KSeF since 1 February 2026 (Article 145l). The rest since 1 April 2026, though until 31 December 2026 they may issue outside the system as long as business invoices in a month stay within PLN 10,000 (Article 145m). In the same period cash registers may print invoices, and receipts with a tax ID up to PLN 450 serve as simplified invoices (Article 145n).

The ministry explains the limit in its questions and answers: the gross value and the month of the issue date count, and once crossed the right to invoice outside KSeF does not return. From 1 January 2027 the KSeF number must appear in transfers between active VAT payers (Article 108g). Details for the smallest businesses are on the KSeF for small businesses page.

An invoice in KSeF is an XML file following the FA (3) template, which since 1 February 2026 has been the only accepted structure. It has fixed blocks: Podmiot1 is the seller, Podmiot2 the buyer, and the Fa section holds dates, line items, totals in the P_13 and P_14 fields for each rate and the amount due in P_15. The ministry publishes the field description on its FA(3) structure page.

Without software such a file is hard to read, so the invoice reader turns it into an ordinary layout, recomputes the totals from the lines and prints to PDF. How to compute the total fields when issuing is explained on the FA(3) e-invoice page. The original remains the XML, kept in the system for 10 years.

The Act provides four special modes. You choose offline24 under Article 106nda for any reason and send the invoice no later than the next working day. During an unavailability announced in the Bulletin the deadline is the next working day after it ends, during a failure 7 working days after it ends, and during a total failure announced in the media invoices are not sent at all. Working days exclude weekends and holidays, including Christmas Eve, a day off since 2025 under the Public Holidays Act.

An invoice handed to the buyer outside the system carries a QR code: one with the KSeF number, or two for an offline invoice, labelled OFFLINE and CERTIFICATE. Read or build the link from the code with the QR code tool, following the ministry page on verification codes.

Article 106ni provides a penalty for an invoice issued outside KSeF despite the obligation, for an offline invoice not following the template and for late sending: up to 100 percent of the invoice VAT, or up to 18.7 percent of the gross amount when the invoice has no VAT. For an invoice of PLN 12,300 with PLN 2,300 VAT the ceiling is PLN 2,300.00. The law applies penalties from 1 January 2027.

On 20 October 2026 the Council of Ministers adopted a bill moving this to 1 January 2028, described in the ministry notice; it is Sejm print no. 3245, not yet law. The KSeF penalties calculator shows both dates.

You log in to KSeF with the trusted profile, an e-ID card, a qualified signature, the company’s e-seal or a KSeF certificate, and software uses a token or certificate. Certificates have been available since 1 November 2025, and old KSeF 1.0 tokens work until 31 December 2026. A company without an e-seal files a ZAW-FA notification. Details are on the token and permissions page.

Before issuing your first real invoice you can practise in the test or demo environment, where invoices have no legal effect. The changes from the previous system version are covered on the KSeF 2.0 page.