KSeF from 1 January 2027: the end of the transition period. Five changes worth preparing for this year

Legal status: 16 September 2026 · Reading time: approx. 20 minutes

Mandatory KSeF (the National e-Invoicing System) has been running since April, but 2026 is a trial year: no penalties, a way out for the smallest businesses, and invoices from a cash register (kasa fiskalna) as before. On 1 January 2027 the way out for the smallest businesses and the one for cash registers close on the same day, while the penalties — according to the Ministry of Finance's announcement of 16 September 2026 — are to wait another year. One of the new rules, moreover, concerns not who issues the invoice but who pays it — and that is the one most often missed by businesses that "already have KSeF sorted".

Below: five changes (in order from the one a small business will feel most), two real-life examples, an end-of-year checklist and an FAQ. If you run a sole proprietorship (JDG — jednoosobowa działalność gospodarcza) or a small limited liability company (sp. z o.o.), this text should be enough to go into January without surprises.

What exactly ends on 31 December 2026

The first four dates all follow from the Act of 5 August 2025, which set the final KSeF timetable (Journal of Laws 2025, item 1203). The fifth is a change of mind by the Ministry of Finance in the summer of 2026 — more on that at the end. On 16 September 2026 the ministry announced that it would postpone the date on which penalties start — more on that in point 4.

1. The PLN 10,000 limit disappears — the last group joins KSeF

Since 1 April 2026 the obligation to issue invoices in KSeF has applied to essentially everyone, but the Act left an exemption for the smallest: anyone who in a given month issues invoices for a total amount of no more than PLN 10,000 gross may, until the end of 2026, do it the old way — on paper or as a PDF. This is used by small service providers, people letting premises to a business (private letting is also a business activity within the meaning of the VAT Act), seasonal businesses, and also many VAT-exempt sole proprietorships that issue two or three invoices a month.

Two things worth knowing about this limit already now:

• Only invoices that would otherwise have to go into KSeF count, that is, those issued to businesses. Consumer sales recorded on a receipt and invoices for private individuals do not count towards the limit.
• Exceeding the limit works like a door with no handle on the inside. The invoice with which the limit was exceeded, and every invoice after it, must already go through KSeF — even if sales fall again the following month.

From 1 January 2027 scale stops mattering. Every invoice issued to a taxable person (apart from a few exceptions, e.g. tickets) goes into KSeF, regardless of whether it is issued by a business with a turnover of PLN 2,000 or PLN 2 million a month, and regardless of whether you are an active VAT taxpayer or use the exemption. What decides is the date of issue, not the date of sale: an invoice for December issued on 2 January is already an invoice in KSeF.

It is worth remembering that the obligation to receive invoices in KSeF has applied to everyone since 1 February 2026. If your supplier has issued an invoice in the system, then it is there — and it is deemed delivered on the day the KSeF number is assigned — even if nobody has opened it yet. Businesses using the PLN 10,000 limit most often have a backlog precisely here.

With a few invoices a month, the free KSeF Taxpayer Application (Aplikacja Podatnika KSeF) is enough; you log in with a Trusted Profile (profil zaufany) or through the mObywatel app. If your accounting office issues invoices on your behalf, it must have been granted permissions in KSeF (e.g. in the KSeF Taxpayer Application) — a formality, but one to deal with before the first January invoice, not after it.

2. The cash register stops being an invoice printer

Until the end of 2026 a mechanism that retail, catering, workshops and petrol stations have grown used to over the years still works: a business customer gives their tax ID (NIP), the cash register prints a receipt showing that NIP, and such a receipt of up to PLN 450 gross is a simplified invoice. Above that amount the cash register can issue an ordinary invoice. Both documents are today excluded from KSeF.

From 1 January 2027 that exclusion expires. A receipt with a NIP stops serving as an invoice, and a sale to a business recorded on a cash register has to be documented with a structured invoice (faktura ustrukturyzowana) in KSeF. The receipt remains in your records as confirmation of the transaction and as the basis for issuing an invoice — nothing more. From that date the Act (Article 111(3a)(1)) no longer provides for an invoice from a cash register. The draft regulation on cash registers published on 26 June 2026 removes the possibility of issuing invoices on a cash register precisely from that date (at the time of writing it is still a draft).

The change affects both sides:

Sellers must have a "receipt → invoice in KSeF" route for business customers. For a shop or a catering outlet this most often means sales software integrated with KSeF, or issuing invoices after hours in the application.

Buyers — and it is this group that usually does not know about the change. If you deal with small business purchases (fuel, a cable, lunch with a business partner) "on a receipt with a NIP", from January such a receipt is no longer a document on the basis of which your accountant can deduct VAT or record the expense as an invoice. You have to give your NIP for the receipt and ask for an invoice, and that invoice will go into KSeF under your NIP. In practice: standing at the till at the petrol station will take a moment longer, but the document will appear in the system and in your books by itself.

The date of issue is again decisive: a receipt with a NIP issued in December 2026 remains a simplified invoice, even if your accountant books it in January.

3. The KSeF number in a bank transfer — an obligation on the payer's side

This is the change that is talked about least, although it affects every business that pays another business by bank transfer.

From 1 January 2027 an active VAT taxpayer who pays another active VAT taxpayer for a structured invoice by bank transfer, or by another instrument that allows a payment reference to be given, must state in that reference the KSeF number of the invoice or the collective identifier assigned by the system (Article 108g of the VAT Act; with a direct debit the obligation rests on the issuer of the invoice). The obligation also covers the situation where the invoice is paid by a taxable person other than the buyer, e.g. a factor.

The KSeF number is not the invoice number from the body of the invoice (FV/12/2027). It is a 35-character identifier assigned by the system at the moment of issue, beginning with the seller's NIP. You will find it in KSeF, in your accounting software, or on the PDF visualisation if the issuer has put it there.

In the split payment mechanism (mechanizm podzielonej płatności, MPP) the change is even more tangible: in the transfer message the invoice number is replaced by the KSeF number. If with one split payment transfer you pay several invoices from a single supplier covering a period of not less than a day and not more than a month, you enter the collective identifier generated in KSeF for that batch of invoices.

When the obligation does not apply:

• payment by card, BLIK, cash or through a payment provider, where there is no "reference" field,
• either party is not an active VAT taxpayer (e.g. you pay a VAT-exempt freelancer),
• an invoice issued offline has not been entered into KSeF because of an announced failure of the system,
• a set-off of mutual claims.

As things stand, the Act provides no separate penalty for the absence of a KSeF number in an ordinary transfer — but the obligation itself will be in force, and in split payment the KSeF number is a statutory element of the transfer message. Why does the state care about this? Because the KSeF number in a transfer closes the loop: invoice, payment and due date in one place. That opens the way to matching invoices with transfers automatically and to picking out those that have not been paid on time — and let us recall that 90 days after the payment deadline has passed, the buyer is obliged to correct the VAT deducted (Article 89b of the VAT Act).

What this means for a small business:

1. Check whether your bank and your software let you enter 35 characters in the transfer reference without truncating them. Most do, but transfer templates containing only the invoice number have to be rebuilt.
2. If you make transfers from a batch exported from your accounting software, this is a task for the software provider — better to ask about it in the autumn than in January.
3. Decide who generates the collective identifiers: you or your accounting office.
4. Before making a transfer you need to know the supplier's VAT status as at the payment date (the white list of VAT taxpayers, biała lista). That determines whether the obligation applies to you at all.
5. There is nothing to stop you from giving the KSeF number in the reference of an ordinary transfer already now. A few months of practice is a comfort you will not have in January.

4. Penalties: what for, how much, and who decides

Under the Act, 2026 carries no penalties. The provisions on financial penalties (Article 106ni of the VAT Act) come into force on 1 January 2027. From that day the head of the tax office imposes a penalty by way of a decision:

• up to 100% of the VAT shown on an invoice issued outside KSeF,
• up to 18.7% of the amount due, if there is no VAT on the invoice (e.g. with an exempt taxpayer).

An arithmetical curiosity: 18.7% is nothing other than 23% VAT "backed out" of the gross amount (23/123). The legislator assumes that tax is embedded in an invoice without VAT as well, and penalises as if it were there.

A penalty may be imposed for three kinds of breach: failing to issue an invoice in KSeF despite the obligation; issuing an invoice that does not conform to the schema in offline24 mode or during a failure or unavailability of KSeF; and failing to send invoices issued offline to the system on time. It is not imposed automatically — its amount is set by a decision of the head of the tax office taking the circumstances into account, so a single technical slip should not end in the maximum. But from January the legal basis for imposing one exists.

Two remarks that temper both panic and complacency:

Penalties do not apply retroactively. An invoice issued outside KSeF contrary to the obligation in 2026 is a breach, but without a financial sanction, and your business partner — as the Ministry of Finance confirms — retains the right to deduct VAT. Invoices in the system are, however, kept for 10 years, so 2026 is not so much "without consequences" as "without penalties".

The date is to be postponed, but for now only in an announcement. In April 2026 the Minister of Finance announced an analysis of extending the penalty-free period, and in June, replying to a parliamentary question, the ministry still pointed to 1 January 2027 as the date on which sanctions would start. On 16 September 2026 the Ministry of Finance announced that it would extend the penalty-free period to 31 December 2027. This requires the Act to be amended, and the ministry is only beginning work on a draft — until the amendment is passed and promulgated, the date in force under the Act is 1 January 2027. Deferring penalties does not remove the obligation: the Ministry of Finance says that KAS (the National Revenue Administration) will react to invoices issued outside KSeF and check whether this leads to an unreliable settlement of tax. We will update this article when the rules change.

5. Tokens are staying — and they were supposed to disappear

This change goes the other way. The original plan was simple: tokens (strings of characters entered into accounting software so that it can talk to KSeF without logging in each time) work alongside KSeF certificates only until 31 December 2026, and from January only certificates remain. After the consultations of June 2026 the Ministry of Finance changed its mind: the updated KSeF 2.0 Manual (Podręcznik KSeF 2.0) provides for tokens to be kept indefinitely, and the ministry additionally proposed the option of setting their validity at between 1 and 365 days.

Who does this matter to? Above all to companies. A KSeF certificate issued in a company's name requires prior authentication with a qualified electronic seal, and that is an expense of over PLN 1,000 plus the time to order and configure it. A token generated by an authorised person (named, for example, in the ZAW-FA notification filed with the tax office) bypasses that route — as does a certificate issued in that person's name. For a sole proprietorship the difference is smaller — the certificate (issued against your PESEL, the Polish personal identification number, and linked in KSeF to the business's NIP) can be downloaded after logging in with a Trusted Profile, free of charge.

Two caveats:

• For now it is the manual that has changed, not the law. The regulation on the use of KSeF is awaiting amendment. If you already have a working integration based on a token, there is no reason to take it apart; if you are in the middle of moving to a certificate, finish the job.
• A certificate is needed in any case for the special modes: offline24, unavailability of the system and failure. A token will not sign an invoice in those modes. A sensible arrangement for a small business is a token for everyday work and a certificate "for a rainy day".

While you are tidying up access rights, check who has permissions to your KSeF (individuals, your accounting office) and whether they are current. Permissions granted electronically in KSeF 1.0 (other than those based on ZAW-FA and owner permissions) had to be granted again — in the Certificates and Permissions Module, or from February 2026 in KSeF 2.0 — and not everyone has done so.

What is not changing (and what gets confused)

• Invoices for consumers stay outside KSeF. You may issue them there voluntarily, but you do not have to.
• Invoices from foreign suppliers — e.g. Microsoft, OpenAI, Figma — as a rule do not go into KSeF. Some services (e.g. Google Workspace) are, however, invoiced by the supplier's Polish company — such an invoice is domestic and arrives through KSeF. For services from abroad you still receive a PDF by e-mail, and the way they are settled (import of services, VAT, withholding tax) is a separate topic that we will write about in a future article.
• Invoices for foreign clients are issued in KSeF, because you are a Polish taxable person, but you deliver them to the client outside the system — most often as a PDF with a QR code that allows the document to be verified in KSeF.
• Offline24 mode has been introduced permanently: you may (for example when you have no connection to the system) issue an invoice conforming to the schema outside it and send it in by the next business day at the latest.
• Corrective notes (noty korygujące) no longer exist. An error on an invoice — including in the buyer's details — is corrected with a corrective invoice, and a mistake in the NIP with a correction to zero and a new invoice.
• The basic time limit for a VAT refund has been shortened from 60 to 40 days — one of the few changes in the KSeF package that works in the taxpayer's favour.

Two examples

Anna runs a VAT-exempt sole proprietorship: she designs interiors and issues three or four invoices a month for a total of about PLN 8,000. In 2026 she stays within the limit and issues PDFs. From 1 January 2027 each of her invoices for a business has to be created in KSeF — the free application and a Trusted Profile are enough for her. Her clients, although they are active VAT taxpayers, do not have to give the KSeF number in their transfers, because Anna is exempt from VAT. If Anna were to issue an invoice outside the system in 2027, the theoretical upper limit of the penalty under the current Act would be 18.7% of the amount due (the Ministry of Finance says there will be no penalties for 2027 yet).

Tomasz is the president of a small technology company, an active VAT taxpayer. In January he pays a marketing agency for five invoices with a single transfer — he needs a collective identifier from KSeF to enter in the reference. He pays for hosting and SaaS tools with the company card — with no KSeF number, because a card has no reference. When filling up the company car, he asks for an invoice to go with the receipt showing the NIP, because from January the receipt alone is no longer a document that his accountant can record as an invoice. The company logs its software into KSeF with the token of Tomasz, who is named in the ZAW-FA notification; for now it is not buying a qualified seal, but Tomasz downloads a certificate in his own name as an authorised person — in case the system fails.

A checklist for the end of 2026

1. Is every invoice for a business created in KSeF? If you use the PLN 10,000 limit, plan the switch for December, not for January.
2. Are you receiving invoices in KSeF? Log in and check whether documents your accountant does not know about are sitting there.
3. Cash register: do you have a "receipt with a NIP → invoice in KSeF" route for business customers? As a buyer: from January you ask for an invoice to go with a receipt showing your NIP.
4. Transfers: do the templates in your bank and the export from your accounting software handle the KSeF number and the collective identifier? Who generates the identifiers?
5. Split payment: prepare, with your bank and your software, a split payment transfer template with the KSeF number (until the end of 2026 the Act still requires the invoice number in split payment transfers).
6. Access rights: who has permissions to your KSeF, whether they are current in KSeF, and whether your accounting office can act on your behalf.
7. Token and certificate: a token for work, a certificate for the emergency modes. A company without a qualified seal can for now stay with a token and the certificate of an authorised person.
8. A failure procedure: who in the business knows what to do when KSeF is down, and who keeps an eye on the deadline for sending in invoices issued offline? Under the current Act, from January, being late on this point is punishable (the Ministry of Finance says penalties will be postponed until the end of 2027).

Frequently asked questions

I am exempt from VAT and issue two invoices a month. Does KSeF apply to me? Yes, from 1 January 2027, with no exemption for small scale — being exempt from VAT does not exempt you from KSeF. Until the end of 2026 you can still use the PLN 10,000 limit.

Can I still send PDFs to clients? You can, but as an extra. The invoice is the document in KSeF; the PDF is its visualisation, convenient for the client and needed with recipients abroad.

What about invoices I issue on a cash register in December 2026? The date of issue decides. A December invoice from a cash register and a December receipt with a NIP are valid as before. An invoice issued in January for a December sale already has to be created in KSeF.

Do I have to give the KSeF number when paying with a company card? No. The obligation covers transfers and other instruments with a "reference" field (with a direct debit — the issuer of the invoice). Payments by card, cash and BLIK without a reference fall outside it.

Is there a penalty for the absence of a KSeF number in a transfer? As things stand, the Act provides no separate sanction for an ordinary transfer without the number. The obligation nevertheless exists, and in split payment the KSeF number is a mandatory element of the transfer message.

How much is the penalty for an invoice issued outside KSeF in 2027? Up to 100% of the VAT on that invoice, or up to 18.7% of the amount due if the invoice does not contain VAT. The specific amount is set by the head of the tax office in a decision. This is the position under the current Act — on 16 September 2026 the Ministry of Finance announced that there will be no penalties for 2027, but that requires the Act to be amended.

I have heard that penalties will be deferred. Is that true? On 16 September 2026 the Ministry of Finance announced that it would extend the penalty-free period to 31 December 2027. This requires the Act to be amended, and the ministry is only beginning work on it, so until the amendment is passed and promulgated the date in force under the Act is 1 January 2027. We will update this text when the rules change.

Do I have to buy a qualified seal for my company? Not if the company has named an authorised person in the ZAW-FA notification, your software connects to KSeF with that person's token, and for the emergency modes you have that person's certificate. A seal is needed when the company itself is to act in KSeF — for example for a token or a certificate issued in the company's name.

How we can help

If we keep your books, KSeF is part of the standard service: we check that all sales invoices are in the system, we download purchase invoices directly from KSeF, and before the end of the year we go through the checklist from this article with you — including transfer settings with the KSeF number and permissions in KSeF.

If you are still looking for an office to take you through January 2027 without penalties and without stress, book a free call. More about how we work with sole proprietorships and with companies.

See also: e-Delivery for sole proprietors: when it becomes mandatory and how to set up your address — the second digital obligation that closes in the same quarter, and 10 things to check before starting a business.

Legal basis: the Act of 11 March 2004 on the tax on goods and services — Article 106ni (penalties), Articles 108a and 108g (the KSeF number in payments and in split payment), Articles 145m and 145n (the PLN 10,000 limit, invoices from cash registers and receipts with a NIP until 31 December 2026), Article 106b(5) and Article 111(3a)(1) (an invoice to accompany a receipt, cash registers from 2027); the Act of 16 June 2023 amending the VAT Act (Journal of Laws 2023, item 1598); the Act of 5 August 2025 (Journal of Laws 2025, item 1203); the KSeF 2.0 Manual and the Ministry of Finance's explanations at ksef.podatki.gov.pl; the Ministry of Finance's announcement of 16 September 2026 on extending the deferral of penalties until the end of 2027. This article is for information only and does not constitute tax advice.