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An invoice in KSeF: how to issue and receive it in a small business

Expert knowledge. Content verified: 7 November 2026.

Invoices from counterparties must be received in KSeF from 1 February 2026, and issued in KSeF from 1 April 2026 (from 1 February 2026 for companies whose sales including VAT in 2024 exceeded 200 million PLN). Companies with invoiced sales of up to 10 000 PLN gross a month have issuing deferred until the end of 2026. You can issue an invoice free of charge in the Ministry of Finance applications or in software connected to KSeF.

Who KSeF applies to and from when

  • Receiving invoices: from 1 February 2026, invoices from counterparties are received in KSeF. The obligation does not apply to, among others, foreign entities and consumers.
  • Issuing: from 1 February 2026 for taxpayers whose sales with VAT in 2024 exceeded PLN 200 million, and from 1 April 2026 for other businesses.
  • Transitional period: if the value of sales documented by invoices in a given month does not exceed 10 000 PLN gross, you do not have to issue invoices in KSeF until the end of 2026. Once the limit is exceeded, the obligation applies from the invoice that exceeded it, and you do not go back to the previous rules.
  • The limit is counted by issue date and gross amounts from invoices that must be issued in KSeF. Not included are, among others, invoices for consumers, invoices from cash registers and receipts with the buyer's NIP up to 450 PLN.
  • From 1 January 2027, using KSeF is to be mandatory for all businesses (Ministry of Finance announcement of 20 October 2026).
  • Excluded are, among others, taxpayers with no seat or fixed place of business in Poland and some special procedures (e.g. non-Union OSS and IOSS import). Invoices to individuals not running a business can be issued in KSeF voluntarily.
  • Proforma invoices, internal invoices, internal documents and credit and debit notes do not go to KSeF.

How to issue an invoice step by step

  1. Log in to the free KSeF Taxpayer Application (browser) or the KSeF Mobile Application. An individual with a NIP has access automatically. A company logs in with a qualified seal or files a ZAW-FA notification naming an individual.
  2. Fill in the seller and buyer details (with the buyer's NIP), items, VAT rates and deadlines. The invoice is created as an electronic document according to the FA(3) schema, in force from 1 February 2026.
  3. Send the invoice to KSeF. The system checks that the XML file conforms to the schema and that the sender has the required permissions, and then assigns a KSeF number, which confirms that the invoice has been accepted.
  4. Download the invoice as XML, HTML or PDF if you need a copy for your records or to send to a buyer who does not use KSeF.
  5. You do not have to pass the KSeF number to the counterparty: the invoice appears in their system automatically and does not require their acceptance.

Issue date and receipt date

  • An invoice sent to KSeF in online mode is issued on the day it is submitted to the system, even when the KSeF number appears the next day.
  • An invoice is received at the moment it is assigned its KSeF number. The date of acceptance is shown in the official confirmation of receipt (UPO).
  • In the offline modes, the issue date is the date entered by the taxpayer in field P_1 of the invoice.

How to receive a purchase invoice

  • An invoice from a counterparty appears in your KSeF without any acceptance on your part.
  • KSeF does not send notifications about new invoices: you have to check for them in the Ministry of Finance application or in software that fetches them automatically.
  • The system does not show the issuer whether the buyer has already downloaded the invoice.

When KSeF is down: offline24 and failures

  • Every taxpayer can issue invoices in offline24 mode: the invoice must be electronic, in the FA(3) format, and reach KSeF without delay, at the latest on the next working day.
  • After an ordinary KSeF failure, announced in the Public Information Bulletin of the Ministry of Finance and in the software, the invoice is submitted within 7 working days of the end of the failure.
  • In the case of a total failure, announced in the mass media, invoices are not submitted to KSeF afterwards.
  • A credit note for an offline24 invoice must also reach KSeF at the latest on the next working day. If it relates to an original invoice from offline24, the original invoice must be sent first so that it receives a KSeF number.

Penalties

The head of the tax office may impose a penalty of up to 100% of the VAT amount on an invoice issued outside KSeF, and where the invoice has no VAT, up to 18.7% of the total amount due. This applies to an invoice not issued in KSeF, issued during a failure not in line with the template, and sent late in offline24 mode. The penalty is paid within 14 days of delivery of the decision (art. 106ni of the VAT Act).

  • In 2026 no penalties are imposed for errors related to the use of KSeF. Under the rules in force so far, penalties are to apply from 1 January 2027 and do not apply retroactively.
  • On 20 October 2026 the Council of Ministers adopted a bill that postpones penalties for KSeF errors to the end of 2027. The bill has moved on to further parliamentary work, so check the Ministry of Finance announcements for its current status. The obligation to use KSeF does not change.

How it works in Zaksio

Anna (AI accountant) and Kasia (AI HR specialist) are software (the AI team), not an accounting firm or a tax adviser. The KSeF integration carries a Beta label in Zaksio: integrations marked Beta are being rolled out together with the first customers.

  • You choose the KSeF environment (test, DEMO or production) yourself in the company settings and connect to it with your own token.
  • You prepare the invoice as a draft, and "Issue invoice" assigns a gap-free number and posts it. On an issued invoice, the "Send to KSeF" button saves the KSeF number and the status "Accepted in KSeF" or the status "Rejected" with a description of the error. Anna proposes sending in the Team inbox, and that always requires your approval.
  • You download purchase invoices from KSeF manually, and for companies with a saved token the AI team also fetches them in the background, every hour. They go to account assignment and approval and are not posted without your decision, unless you deliberately switch on automatic mode.
  • VAT amounts and totals are calculated by deterministic code, not AI.
  • The Start plan is free within limits, and the details are in the pricing page.

Sources

  • Act of 11 March 2004 on Value Added Tax (consolidated text Dz.U. 2025 poz. 775, as amended), art. 106ga, 106gb, 106ni — https://isap.sejm.gov.pl/isap.nsf/DocDetails.xsp?id=WDU20040540535
  • National e-Invoicing System (KSeF), Scope of mandatory KSeF — https://ksef.podatki.gov.pl/informacje-ogolne-ksef-20/zakres-obowiazkowego-ksef/
  • National e-Invoicing System (KSeF), Legal basis and key deadlines — https://ksef.podatki.gov.pl/informacje-ogolne-ksef-20/podstawy-prawne-oraz-kluczowe-terminy/
  • National e-Invoicing System (KSeF), offline24 mode — https://ksef.podatki.gov.pl/informacje-ogolne-ksef-20/tryb-offline24/
  • National e-Invoicing System (KSeF), KSeF 2.0 questions and answers — https://ksef.podatki.gov.pl/pytania-i-odpowiedzi-ksef-20/
  • National e-Invoicing System (KSeF), Rules of KSeF application and legal provisions (27.04.2026) — https://ksef.podatki.gov.pl/ksef-news/zasady-obowiazywania-ksef-i-przepisy-prawne/
  • Ministry of Finance, Council of Ministers in favour of deferring penalties for KSeF errors (20.10.2026) — https://www.gov.pl/web/finanse/rada-ministrow-za-odroczeniem-kar-za-bledy-w-ksef-i-przedluzeniem-odwrotnego-obciazenia-vat
  • Biznes.gov.pl, National e-Invoicing System (KSeF) — https://www.biznes.gov.pl/pl/portal/004651

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