KSeF in Poland: what it is, deadlines, penalties and how to prepare for 1 January 2027

In short. KSeF (Krajowy System e-Faktur, Poland’s National e-Invoicing System) is the mandatory Ministry of Finance platform for invoices between businesses. Large companies switched on 1 February 2026, the rest on 1 April 2026. Firms invoicing businesses for up to 10,000 zł a month switch on 1 January 2027. Receiving invoices through KSeF has been mandatory for everyone since 1 February 2026.

The 10,000 zł limit is counted separately for each month, and invoices to foreign clients count towards it. Take an IT contractor running a JDG (jednoosobowa działalność gospodarcza, a Polish sole proprietorship) who bills a client abroad 20,000 zł a month. KSeF has been mandatory for them since their first such invoice after 1 April 2026. Under the law, the penalty for an invoice issued outside the system is up to 100% of the VAT on it, or up to 18.7% of the total on an invoice without VAT. It will be applied from 1 January 2027. A Ministry of Finance draft published on 23 September 2026 proposes moving the penalties to 2028. It leaves the obligation to use KSeF from 1 January 2027 untouched.

Dates and rules in this guide are as of 28 September 2026. KSeF rules have changed several times, so check the sources at the end before you decide.

What is KSeF? Poland’s e-invoicing system in plain English

KSeF stands for Krajowy System e-Faktur, which translates into English as the National e-Invoicing System. It is a Polish Ministry of Finance service in which businesses issue, receive and store invoices. An invoice in KSeF is an XML file built on the government FA(3) schema, and it becomes a legal document once the system assigns it a KSeF number.

The first habit to drop is treating the PDF in your inbox as the original. Formally, the document is now the XML in the system, and the PDF is just a readable copy of it. When an invoice is passed on outside KSeF, the copy carries a QR code with the KSeF number, and anyone can use it to verify the document.

We can help you solve any task!

Stanislav Tsys

Head of UniConsulting

Get consultation

Are you planning to start a business in Poland? Start a company or a private enterprise? We will help you bring your business to the Polish market from scratch until the first sales. We will develop: a strategy for entering the Polish market, open a remote legal entity or IE, will do accounting and registration of your employees. Leave an application for introductory consultation

What this changes in your day-to-day work:

• An invoice counts as issued on the day it is sent to the system and as received on the day it is assigned a KSeF number. The buyer does not have to confirm receipt.
• An accepted invoice cannot be edited. Mistakes are fixed with a corrective invoice (faktura korygująca), and you can issue as many corrections as you need. Noty korygujące, the corrective notes that buyers used to issue, were abolished on 1 February 2026.
• The system stores invoices for 10 years, so you do not need to print them for your archive.
• KSeF does not notify you about incoming invoices. You have to check for them yourself in the app or through your invoicing software.

The mandatory details on an invoice have not changed. They are covered in our article on the VAT invoice.

When KSeF becomes mandatory: 2026–2027 deadlines

KSeF in Poland is being rolled out in stages, and one mistake is worth ruling out straight away: the idea that small businesses as a whole move to KSeF in 2027. Since 1 April 2026, the obligation has covered every VAT payer and every business exempt from VAT. The postponement to 2027 applies only in the months when your invoices to businesses add up to no more than 10,000 zł gross.

The limit is counted on gross amounts, that is including VAT, and only on invoices you are obliged to issue in KSeF. Invoices to private individuals, cash register sales and receipts with a NIP up to 450 zł do not count towards it. An invoice belongs to the month of its issue date, even if the sale itself took place earlier.

Once you exceed the limit, you lose the right to invoice outside KSeF, starting with the invoice that took you over it. Every invoice after that, until the end of the year, goes through the system, even if your sales drop the following month.

Important. The 10,000 zł postponement ends the first time you exceed the limit. After that, you cannot go back to invoicing outside KSeF in 2026.

Being exempt from VAT does not take you out of KSeF. If a JDG without VAT issues an invoice to a business, whether at the client’s request or on its own initiative, that invoice goes through the system on the same timeline. You cannot replace it with a rachunek (a simple bill), because a rachunek is meant only for activities outside the scope of VAT.

Businesses with cash registers may issue cash register invoices and receipts with the buyer’s NIP up to 450 zł outside KSeF until 31 December 2026. From 1 January 2027, an invoice to a business for a cash register sale is issued through the system.

The deadlines have moved before, from 1 July 2024 to 1 February 2026, and the act of 5 August 2025 split the rollout into stages. The dates in the table were checked against the Ministry of Finance portal ksef.podatki.gov.pl as of 28 September 2026.

Who does not have to use KSeF

KSeF does not apply to invoices issued to private individuals or to sellers without a fixed establishment in Poland. A few special VAT procedures and certain documents listed in a Ministry of Finance regulation are also excluded. Every other invoice between businesses goes through the system, including invoices to foreign buyers, which matters most if you are an IT contractor with clients abroad.

According to the Ministry of Finance portal, these are issued outside KSeF:

• Invoices to private individuals who do not run a business. The seller may issue them in KSeF voluntarily, and the same applies to purchases an entrepreneur makes for personal needs.
• Foreign sellers without a fixed establishment in Poland, even if they have a Polish VAT number. They may use KSeF voluntarily.
• Special procedures. These are non-EU OSS and import OSS (IOSS), the simplified VAT schemes for sales within the EU and for imports. The list also covers occasional international bus transport and the SME scheme, under which small businesses from other EU countries sell in Poland without VAT. Invoices under these procedures cannot be issued in KSeF, even voluntarily.
• Documents listed in the Ministry of Finance regulation of 7 December 2025. These include travel tickets that serve as invoices, motorway toll receipts, insurance policies and some financial services invoiced with a simplified invoice. Self-billing is also excluded when a foreign buyer without a Polish NIP issues the invoice on behalf of the Polish seller.
• Documents that are not invoices. A proforma, internal documents, accounting notes and a rachunek for activities outside VAT are not sent to KSeF.

The riskiest confusion here concerns foreigners. The exclusion covers a foreign seller, but a foreign buyer is not on the list of exceptions in the VAT Act (art. 106ga ust. 2). This is why a Polish JDG or Sp. z o.o. issues an invoice to a client in Germany or the US in KSeF. The client cannot log into the system, so the invoice is delivered in an agreed way, for example as a PDF by email. The PDF carries a QR code with the KSeF number, which the client can use to verify the document.

Important. You may come across the claim that export invoices do not go through KSeF. Under the law, they do. The only difference is delivery: the client receives a PDF with a QR code.

How to prepare for KSeF before 1 January 2027: a checklist

Preparing for KSeF comes down to seven steps, and the first three are about access to the system. Almost all of it can be done free of charge with Ministry of Finance tools. If an accountant issues your invoices, you are left with the first three steps and an agreement with them on who handles incoming invoices.

1. Find out which stage applies to you. Export your invoices to businesses for each month of 2026 and add up the gross amounts. Include invoices to foreign clients, and leave out invoices to private individuals and cash register invoices. If the total went over 10,000 zł in at least one month after 1 April, KSeF is already mandatory for you. If not, your final deadline is 1 January 2027. You will find the figures in the sales register of your invoicing software or with your accountant. This step costs nothing, and all you need is a list of invoices with their issue dates.

1. Decide who issues invoices and grant permissions. The owner of a JDG gets KSeF permissions automatically through their NIP and does not have to file anything. A Sp. z o.o. logs into the system with a qualified electronic seal. If it has no seal, the company files a ZAW-FA notification with the urząd skarbowy (tax office) and names one person in it. That person then grants permissions to everyone else, including to an accounting firm as a whole, which will then distribute them among its staff. Permissions are granted free of charge in Aplikacja Podatnika KSeF (the KSeF Taxpayer App) or in software connected to the system. ZAW-FA is filed through e-Urząd Skarbowy (the tax office’s online account), or on paper in person or by post, but since 1 January 2026 no longer through ePUAP (the government e-services platform). Permissions under ZAW-FA start working once the tax office enters them into the system, and if you file by post, add delivery time on top. You will need the company’s NIP, the details of the authorised person and the signatures of those who represent the company under the KRS (the National Court Register). If you would rather hand issuing and receiving invoices to a specialist, a Uniconsulting accountant will take KSeF on and set up access permissions. How this kind of service works is explained in our guide to choosing an accountant.

1. Set up how you log in. The Ministry of Finance regulation allows five login methods, and not all of them are free.
2. Government electronic identification through login.gov.pl: Profil Zaufany (Trusted Profile), mObywatel (the government mobile app), bank login or e-dowód (electronic ID card). It is free but requires a PESEL (Polish personal identification number). Profil Zaufany can be confirmed through online banking and is valid for 3 years.
3. A qualified electronic signature, bought from a commercial provider. If the signature does not contain your PESEL and NIP, its details are registered with the tax office through ZAW-FA.
4. A qualified electronic seal, which companies use.
5. A KSeF certificate, issued in the system itself after your first login with one of the methods above. It is valid for up to two years. Type 1 is used to log in, and type 2 is needed for offline invoices.
6. A token, a key string your software uses to log into KSeF. Under the regulation, tokens work until 31 December 2026, although the Ministry of Finance announced on the KSeF portal that it will keep them indefinitely. As of 28 September 2026 the regulation has not been amended, so ask your software provider whether it can work with a KSeF certificate.

A JDG owner grants permissions to their accountant in the system personally, so they need at least one login method in any case.

1. Choose where to issue invoices. The Ministry of Finance offers three free tools. Aplikacja Podatnika KSeF runs in the browser at ap.ksef.mf.gov.pl, and in it you issue, receive and correct invoices, grant permissions and generate certificates. The KSeF mobile app is available on Google Play and the App Store. E-mikrofirma, inside e-Urząd Skarbowy, transfers invoices straight into your VAT register, but you log into it through login.gov.pl or mObywatel. Paid invoicing software will work too, as long as it is connected to KSeF 2.0 (the current version of the system) and supports certificates. Check KSeF 2.0 support with the provider before you commit.

1. Agree on the process with suppliers and customers. Suppliers who already use KSeF issue your invoices in the system, and the PDF they email you is only a copy. The date of receipt is the day the KSeF number is assigned. Tell your foreign clients in advance that invoices will arrive as a PDF with a QR code.

1. Practise without consequences. The Ministry of Finance runs a test version of Aplikacja Podatnika (ap-test.ksef.mf.gov.pl) and a demo version (ap-demo.ksef.mf.gov.pl). Do not enter real company data in the test version. In the demo version, logging in works the same way as in the live system. Invoices have no legal effect in either of them. There are no penalties at all in 2026, so you can already start issuing your first real invoices in KSeF.

1. Prepare offline mode and your 2027 payments. Generate a type 2 KSeF certificate in advance, because you will need it when the system fails. From 1 January 2027, when an invoice between VAT payers is paid, the KSeF number must be included in the transfer title. Check whether your bank or software fills it in for you.

KSeF penalties: what happens if you skip the system

There are no KSeF penalties in 2026. Under current law they apply from 1 January 2027. For an invoice issued outside KSeF, the tax office can impose a fine of up to 100% of the VAT shown on it. If the invoice carries no VAT, the fine is up to 18.7% of its total amount.

A penalty applies if an invoice was not issued in KSeF when it had to be, was issued offline without following the schema, or was not sent to the system on time. It is imposed by a decision of the naczelnik urzędu skarbowego (head of the tax office) and must be paid within 14 days of delivery. These breaches do not lead to fiscal criminal proceedings.

To get a sense of scale, take an invoice for 12,300 zł gross at the 23% rate. The VAT on it is 2,300 zł, so the fine for issuing it outside KSeF is up to 2,300 zł. For a JDG without VAT, an invoice for 10,000 zł means a fine of up to 1,870 zł.

On 16 September 2026, the Ministry of Finance announced that it wants to postpone the penalties by a year. On 23 September, draft act no. UD477 appeared on the website of the Government Legislation Centre (Rządowe Centrum Legislacji). Under the draft, penalties would apply from 1 January 2028. As of 28 September 2026, the draft is going through consultations and the Sejm has not passed it.

Plan by the law as it stands: switch to KSeF by 1 January 2027 as if the penalties start on that date. The draft only postpones the penalties. The 10,000 zł limit and the cash register exceptions still end on 31 December 2026, and the draft does not extend them. The Ministry of Finance has also warned that in 2027 KAS (the National Revenue Administration) will send reminders about KSeF. Businesses that ignore them will be checked for whether their VAT settlements are distorted.

Important. Moving the penalties to 2028 is only a draft for now. It does not cancel the obligation to issue invoices in KSeF from 1 January 2027.

Penalty information is as of 28 September 2026. You can check whether the postponement has been adopted on ksef.podatki.gov.pl and in Dziennik Ustaw (the Journal of Laws).

What to do if KSeF is down

If KSeF is down, you issue the invoice offline on the same FA(3) schema and send it to the system later. Each mode has its own deadline for sending, from the next business day up to seven business days after the outage ends. Only in a total outage announced in the media are invoices issued on paper or as a PDF and never sent to KSeF at all.

The issue date of an offline invoice is the date stated on the invoice itself. A buyer with a Polish NIP receives it in KSeF on the day the number is assigned. If an invoice issued online was only sent to the system the next day, it is automatically treated as an offline24 invoice. You do not have to prove that your internet was down.

Tip. Generate a type 2 KSeF certificate in advance. Without it, you cannot put the second QR code, marked CERTYFIKAT, on an offline invoice for your client.

Outages do happen already: on 25 September 2026, the Ministry of Finance reported disruptions in Aplikacja Podatnika KSeF. Notices about maintenance and outages are published on ksef.podatki.gov.pl.

KSeF FAQ

Do I need KSeF if my JDG is not VAT-registered?

Yes, if you invoice businesses, because a VAT exemption does not take you out of KSeF. The deadline is the same: 1 April 2026, or 1 January 2027 if your invoices stay within 10,000 zł a month. Invoices to private individuals can be issued outside the system. For the wider picture of JDG taxes, see our article on sole proprietor taxes. If you work in IT, see also how to choose a tax form for a JDG in IT.

How do I send an invoice to a foreign client?

Issue it in KSeF and send the client a PDF by email or another agreed method. The PDF must carry a QR code with the KSeF number, which the Ministry of Finance app or your invoicing software adds.

Can I keep issuing invoices in Word or Excel after 2026?

Not to businesses: from 1 January 2027 this is allowed only during a total KSeF outage. For private individuals and in the other exceptions, an invoice in Word, Excel or PDF remains legal. In 2026, Word is acceptable as long as your invoices to businesses for the month have not gone over 10,000 zł.

Does a proforma invoice have to go through KSeF?

No. Under the VAT Act a proforma is not an invoice, so it is not sent to the system. More on this in our article on the proforma invoice.

I only receive invoices. Do I need to do anything?

Yes, you need to set up access, because suppliers who use KSeF issue your invoices in the system, and it does not send notifications. You can log into Aplikacja Podatnika yourself, use software that downloads invoices automatically, or grant permissions to your accountant.

Who gives my accountant access to KSeF?

In a JDG, the owner does it in Aplikacja Podatnika KSeF or in their software. In a Sp. z o.o., access is granted by the holder of the qualified seal or by the person named in ZAW-FA. Permissions can be given to an accounting firm as a whole, and the firm will distribute them among its staff.

How do I correct a mistake in a KSeF invoice?

Only with a corrective invoice, which is also issued through KSeF. An accepted invoice cannot be changed, and corrective notes were abolished on 1 February 2026. There is no limit on the number of corrections.

Need help with KSeF?

KSeF is easiest to handle when one person is responsible for both issuing and receiving invoices. Uniconsulting accounting will check which stage your business falls into and set up access permissions. It can also take over issuing and receiving your invoices in KSeF.

This article is for information only and does not replace advice from an accountant or tax adviser. Deadlines, penalties and login methods are given as of 28 September 2026. KSeF rules have changed several times since 2022, so check ksef.podatki.gov.pl before making a decision.