KSeF for beginners – what it is and who it affects

KSeF (the national e-invoicing system) is a central register of invoices kept by the Ministry of Finance. From 1 February 2026 it is mandatory for the largest VAT payers, and from 1 April 2026 for all other taxpayers, including those exempt from VAT. If you run a company, it almost certainly applies to you. The transitional exceptions (among others for companies with invoices up to PLN 10,000 gross a month) end on 31 December 2026.

This article is for people who are hearing about KSeF for the first time or who have only seen headlines about a “big change in VAT”. We explain from the basics – what it is, what it is for, how it works and what it changes in your everyday work.

What KSeF is

KSeF is an IT system of the Ministry of Finance at ksef.mf.gov.pl. Its role is to:

1. Receive invoices from issuers (sellers) in XML format
2. Validate – check whether the invoice is filled in correctly, whether the NIPs (tax identification numbers) exist and whether the data adds up mathematically
3. Assign a KSeF number – a unique identifying number, which is an addition to the invoice number given by the issuer and not a replacement for it
4. Make it available to the recipient – the buyer has the invoice in KSeF from the moment it is given a KSeF number
5. Store – the system stores invoices sent to KSeF for 10 years from the end of the year in which they were issued – for VAT purposes you do not have to archive them separately. Other documents (receipts, invoices from outside KSeF, such as foreign ones, contracts, statements) you continue to keep for the periods in the Accounting Act and the Tax Ordinance Act.

As a result, the whole flow of invoices between companies in Poland goes through one channel – the ministry’s. There are no more “invoices in emails”, “invoices in Dropbox”, “invoices on a receipt”. One invoice = one document in KSeF.

Why it was introduced

KSeF has three main aims:

• Reducing the VAT grey economy – the tax authorities see every invoice in real time and can compare it with JPK_V7 returns (the monthly file with the VAT settlement); VAT carousel fraud becomes much harder
• Simplification for companies – the system stores invoices sent to KSeF for 10 years from the end of the year in which they were issued, so for VAT purposes you do not have to archive them separately; from 1 February 2026 the basic VAT refund period is 40 days (Article 87(2) of the VAT Act) – this is a general change, not a reward for using KSeF
• Standardising the process – one invoice format across the whole economy, instead of dozens of different templates in different industries

What an invoice in KSeF looks like

Instead of a PDF that you send by email, you create an XML document in line with the FA(3) schema. It contains the same data as a paper invoice:

• the issuer’s details (NIP, name, address)
• the buyer’s details (NIP, name, address)
• the invoice line items (name, quantity, price, VAT)
• the total net, VAT, gross
• the date of issue and the date of sale
• the invoice number (given by your program)

In addition, after acceptance KSeF assigns a KSeF number. It does not replace the invoice number given by the issuer – the invoice has both. In dealings with customers you still use your own invoice number (FV/2026/04/001), and the KSeF number is given, among other places, in a corrective invoice, and from 2027 also in transfers for invoices.

How KSeF changes everyday work

Before KSeF you issued an invoice in your program (or in Word), generated a PDF and sent it by email. The recipient printed it or imported it into their program.

With KSeF:

1. You issue the invoice in your program
2. The program automatically sends the XML to KSeF
3. KSeF checks the invoice and assigns a number (seconds)
4. Your program downloads the confirmation with the KSeF number
5. The recipient sees the invoice in their KSeF panel automatically

You no longer have to send an email with a PDF. You no longer have to collect confirmations of receipt. The day the KSeF number is assigned is the day the buyer receives the invoice (Article 106na(3) of the VAT Act) – on which, among other things, the earliest period for deducting VAT depends.

What does not change

Some things stay as they were:

• B2C invoices (for consumers) – still PDF/paper, unless the consumer gives a NIP
• Fiscal receipts – the cash register works independently; receipts are outside KSeF
• Foreign invoices – an invoice for a foreign buyer (for example, an intra-Community supply of goods, WDT) you issue in KSeF, and the buyer gets it outside the system, with a QR code; the buyer has no access to KSeF
• Invoices from cash registers and receipts with a NIP up to PLN 450 (simplified invoices) – may be outside KSeF until 31 December 2026; from 2027 – in KSeF
• OSS / IOSS – e-commerce sales to consumers in the EU are outside KSeF
• JPK_V7 – you still submit the monthly JPK, but it is a register kept by you; KSeF supplies the invoices, and you (or your accounting firm) still create the register and the markings

Permissions – who can do what in the company

In your company, access to KSeF is held by the people to whom you grant permissions. By default – nobody except the owner/board. In the KSeF panel you can add:

• An accounting firm – access to issue and receive invoices to the extent you grant
• An accounting employee – receiving purchase invoices only
• A sales employee – issuing invoices only
• An invoicing program – technical access (a KSeF certificate or a token) for automatic integration

The details of permissions are in the article KSeF in an accounting firm.

What you must do if you do not have KSeF yet

1. Check your invoicing program – it must support KSeF and the FA(3) structure
2. Get access to the KSeF panel – log in, for example, with a Trusted Profile at ksef.mf.gov.pl
3. Assign permissions to people on your team and to the accounting firm
4. Issue your first test invoice – see the article How to issue your first invoice in KSeF

What next

You can stay with your own invoicing program – at Profais we help with the KSeF implementation and with granting permissions, and as part of our accounting service we fetch your invoices from KSeF for posting. If you have doubts about the program or the permissions, get in touch with us. See also our KSeF service.

Sources: ksef.mf.gov.pl, ksef.podatki.gov.pl, podatki.gov.pl, the VAT Act (Articles 106ga–106nha).