KSeF mandatory e-invoicing in Poland: deadlines

Woman holding an invoice at a laptop with a spreadsheet

10Sep

FORTUNKA
KSeF
September 10, 2026

The National e-Invoicing System (Krajowy System e-Faktur, KSeF) is no longer a plan for the future. Since 1 February 2026 the largest taxpayers issue their invoices in KSeF, and since 1 April 2026 — all remaining VAT-registered businesses. The last group, the smallest firms, joins on 1 January 2027. Below we set out what this means for a small business today, what has been deferred to the end of 2026, and what working with an accounting office in KSeF looks like.

What is KSeF?

KSeF is a Ministry of Finance system in which invoices are issued, sent and stored in a single format (the structured invoice). Instead of e-mailing a PDF, you send the invoice to KSeF; the system assigns it a number, makes it available to the buyer and stores it. The issue date is the date the invoice is sent to KSeF. The legal basis for the obligation is the Act of 5 August 2025 amending the VAT Act (Dz.U. 2025 poz. 1203), together with the implementing regulations of December 2025.

Who does it apply to?

The obligation covers businesses issuing invoices in Poland — both active VAT payers and those exempt from VAT. It concerns invoices between businesses (B2B). Invoices for consumers (B2C) may be issued in KSeF voluntarily; there is no obligation.

Dates

The obligation came into force in stages, and for most businesses it already applies:

1 February 2026 — businesses whose sales including tax exceeded 200 million PLN in 2024.
1 April 2026 — all other businesses, including sole proprietorships and small companies.
1 January 2027 — the smallest firms: those whose total monthly sales including tax do not exceed 10,000 PLN may issue invoices on paper or electronically outside KSeF until the end of 2026. The limit is counted by the invoice issue date; the invoice that exceeds it, and every invoice after it in that month, must go to KSeF.

Transition period until 31 December 2026

A few obligations only come into force on 1 January 2027:

Penalties for breaching KSeF obligations — they apply from 1 January 2027.
The KSeF number in the bank transfer — from 1 January 2027, an active VAT payer paying another active VAT payer for a KSeF invoice gives its KSeF number (or a collective identifier) in the transfer.
Receipts with a NIP up to 450 PLN treated as simplified invoices, and invoices from cash registers — allowed until 31 December 2026; from 1 January 2027 invoices can no longer be issued from a cash register.
The offline24 mode — when there is no connection to KSeF, an invoice can be issued outside the system and sent to KSeF no later than the next business day.

KSeF tokens stay — what the Ministry of Finance decision changes

At the start of 2026 the rule was still that tokens for authentication in KSeF would disappear: § 13 of the regulation of 12 December 2025 on the use of KSeF (Dz.U. 2025 poz. 1815) allows them only until 31 December 2026, and from 2027 only KSeF certificates were to remain. After the consultations of June 2026 the Ministry of Finance changed its mind: on 1 September 2026 it announced that tokens would be kept indefinitely and that the regulation would be amended. Until the amendment, the provision still says 31 December 2026 — so it is worth checking this before the end of the year. In practice: a token generated in KSeF 2.0 (from 1 February 2026) stays valid until revoked and works in interactive and batch sessions through the API or an invoicing program, but it does not log you in to the KSeF Taxpayer Application. Tokens from KSeF 1.0 do not work in KSeF 2.0 — you have to generate new ones. It is also worth knowing that the offline24 mode (Article 106nda of the VAT Act) is a permanent solution, not a transitional one: an invoice can be issued outside the system and sent to KSeF no later than the next business day, with no end date.

What does this mean for a small business today?

Invoices from contractors who already invoice in KSeF do not arrive by e-mail — you have to collect them from the system and check there whether they have come in. Sales invoices are issued in a program connected to KSeF or directly in the Ministry of Finance application. For an accounting office to act on your behalf, you grant it permissions in KSeF — a sole proprietorship does this itself after logging in, a company through a qualified electronic seal or the ZAW-FA form filed with the tax office.

What we do in KSeF for clients

We help you grant the office permissions (ZAW-FA or a seal), we check whether your invoicing program sends and receives documents through KSeF, we collect purchase invoices from KSeF and post them as part of our bookkeeping services, we prepare JPK_V7, and before 1 January 2027 we sort out payments with you so that the KSeF number reaches your transfers.

Not sure whether your business fits within the 10,000 PLN limit, or have you been invoicing in KSeF since April and want to hand the collection and posting of documents to an accounting office? Write to us — we will look at your situation and agree what needs to be done.