KSeF (Krajowy System e-Faktur, the National e-Invoice System) is Poland's government platform for issuing and receiving invoices, and it became mandatory in stages through 2026. If you invoice other businesses in Poland, whether through a JDG or a company, you need software that can send and receive invoices through it. This guide explains what KSeF is, who has to comply and when, and what the penalties look like if you do not, based on the rules in force in 2026.
What KSeF is
KSeF is a platform run by the Ministry of Finance for issuing and receiving invoices. It has existed as a voluntary option since 2022, and became mandatory in stages during 2026.
Every invoice issued through KSeF receives a unique KSeF number assigned by the Ministry of Finance, and is stored by the system for 10 years, so you no longer need to archive paper or PDF copies yourself. In practice, this replaces emailing PDF invoices for domestic B2B counterparties: the invoice exists in KSeF as an XML file, and a Polish business counterparty retrieves it directly from the system through their own software, with no need for you to send it yourself. Foreign buyers without a Polish NIP cannot retrieve invoices from KSeF the same way, so you still need to deliver the invoice to them directly.
Rollout schedule: who has to comply, and when
| Stage | Date | Applies to |
|---|---|---|
| Stage 1 | February 1, 2026 | Large companies (2024 gross sales above 200 million PLN) |
| Stage 2 | April 1, 2026 | All other active VAT payers, and VAT-exempt taxpayers issuing B2B invoices |
| Stage 3 | January 1, 2027 | Micro-businesses with sales up to 10,000 PLN/month (deferral option) |
Regardless of your own issuing deadline, you needed to be able to receive invoices from suppliers through KSeF starting February 1, 2026. That obligation applies to essentially every taxpayer, with only statutory exceptions, no matter the size of your business, so make sure your invoicing software can pull incoming invoices from KSeF even before your own issuing obligation begins.
Who KSeF applies to
- Every VAT-registered business, for its B2B invoices.
- VAT-exempt businesses too: a JDG or company using the 240,000 PLN/year exemption still has to issue B2B invoices through KSeF.
- Companies of any legal form holding a Polish NIP, including sp. z o.o., general partnerships and limited partnerships.
When it does not apply:
- B2C sales: invoices to consumers can still be issued as PDF or paper.
- Foreign entities without a Polish NIP.
- Intra-EU supplies and exports, pending separate EU-wide rules.
- Emergency ("OFF") mode invoices issued during a system outage, as long as they are sent to KSeF once the system is back.
Correction notes are gone for KSeF invoices
As of February 1, 2026, the "correction note" (nota korygująca), previously used by a buyer to fix a minor error on a seller's invoice, can no longer be used for invoices issued through KSeF. For those invoices, even a small mistake, such as a typo in an address, requires the seller to issue a proper corrective invoice (faktura korygująca) through KSeF.
What a KSeF invoice actually is
A structured invoice is an XML file matching the FA(3) schema published by the Ministry of Finance. Every field, the invoice number, the date, the buyer's NIP, the amounts, has a defined place within that structure. Once sent, the invoice receives a KSeF number, which then has to appear in your VAT records, in the NrKSeF field, and often in payment references too. You do not need to understand the XML format yourself: invoicing software integrated with KSeF, like Plumm, generates it automatically.
How to issue KSeF invoices
- Integrated accounting software (recommended): you issue the invoice as normal, and the software converts it to XML, sends it to KSeF, and retrieves the KSeF number, with no manual steps on your part.
- Aplikacja Podatnika KSeF, the Ministry's free web app at podatki.gov.pl: manual entry, with no link to your own bookkeeping.
- A mobile app, for iOS and Android: suited to businesses issuing very few invoices a month.
- e-Urząd Skarbowy (e-mikrofirma): a tax-office portal aimed at micro-businesses.
KSeF and your VAT filings
Since February 1, 2026, the JPK-V7M(3) and JPK-V7K(3) structures, Poland's standard VAT audit file formats, include a dedicated KSeF field. Every invoice in your VAT records needs its KSeF number attached, in the NrKSeF field. The tax office can automatically cross-check your JPK filing against the KSeF database, and any mismatch, a missing number or a wrong amount, triggers a request to correct it.
The emergency "OFF" mode
If the Ministry's system is down, whether from an outage or scheduled maintenance, you can issue an invoice outside KSeF, marked with the code OFF, and you must send it to KSeF as soon as the system is restored. You report it with the OFF marking in your JPK-V7, and a missing KSeF number is accepted in that specific case.
Two other substitute codes appear alongside OFF in JPK-V7(3) filings: BFK, for invoices genuinely outside the KSeF requirement, such as B2C invoices issued as PDF, invoices from a foreign counterparty without a Polish NIP, or invoices from before your own KSeF obligation started, and DI, for documents that are not invoices at all, such as internal documents for intra-EU acquisitions. A common mistake is issuing a domestic B2B invoice through old software, with no actual system outage, and marking it BFK. That is incorrect: a B2B invoice covered by the KSeF obligation has to actually go through KSeF, and BFK is not a way around that.
Penalties: what happens if you skip KSeF
February 1 to December 31, 2026 is a transitional period with no monetary KSeF penalties for issuing invoices outside the system, even though the obligation to issue through KSeF is already in force on a staged basis (February 1 for the largest companies, April 1 for everyone else). This is a grace period for rolling out the new process, not a permanent exemption. General liability for improperly issued invoices, under Poland's Fiscal Penal Code, can still apply depending on the circumstances.
From January 1, 2027, an administrative sanction of up to 100% of the VAT shown on an invoice issued outside KSeF applies, or on one with errors that make it impossible to identify. If the invoice shows no VAT at all, the sanction is up to 18.7% of the total amount owed instead. There is no statutory upper cap in złoty. As an example: an invoice for 100,000 PLN net, with 23,000 PLN of VAT, issued outside KSeF after that date could carry a penalty of up to 23,000 PLN for that single invoice.
Separately, a missing KSeF number in your JPK-V7 records, on an invoice that was otherwise issued correctly, triggers a request to correct the filing, and an uncorrected formal error carries its own, smaller penalty of up to 500 PLN. That is a distinct rule from the KSeF sanction above, not an alternative version of it.
Buyers are not automatically penalized either: a missing KSeF number on a seller's invoice does not by itself strip the buyer of their right to deduct VAT, that is governed by the ordinary conditions in the VAT Act. Even so, it is good practice to ask sellers for a properly KSeF-issued invoice, to avoid disputes over evidence later.
A practical compliance checklist
- Issue invoices only through KSeF-integrated software, for automatic XML generation.
- Confirm every invoice actually receives a KSeF number.
- Make sure the KSeF number is recorded and appears in your JPK-V7.
- Set up an API token so you can receive supplier invoices automatically.
- Confirm your software supports OFF mode and applies it correctly during outages.
- Issue all corrections as proper corrective invoices through KSeF, since correction notes no longer exist.
Common questions
Do I have to use KSeF if I am not VAT-registered? Yes, if you issue B2B invoices. Since April 1, 2026, the KSeF obligation applies whether you are an active VAT payer or using the VAT exemption. The exception is the smallest businesses: those with monthly sales up to 10,000 PLN can defer the obligation until January 1, 2027.
Do invoices to consumers need to go through KSeF? No. B2C invoices, for individuals not running a business, can still be issued as PDF or paper.
What about invoices I issued before my KSeF obligation started? They remain valid. There is no requirement to send them to KSeF retroactively.
How long does KSeF keep my invoices? 10 years from the date of issue. The Ministry of Finance archives them, so you do not need to keep your own copies.
Can I issue a proforma invoice through KSeF? No. A proforma is not a VAT invoice, so it is issued outside KSeF, as before, in PDF or paper form. Once you are paid, you issue the actual invoice through KSeF.
Once you are registered (see our JDG registration guide) and start invoicing, KSeF compliance is not optional, so it is worth setting up the right software early. If you are deciding between a JDG and a company, our guide to company taxes in Poland covers how the VAT and CIT obligations compare.
Every invoice issued in Plumm is sent to KSeF automatically, with the KSeF number recorded in your VAT records and JPK-V7 for you. Start a free trial.
This article is general information, not tax advice, and reflects the rules in force in 2026. Filings with Polish tax authorities, including JPK-V7, are submitted in Polish.