KSeF (Krajowy System e-Faktur) is the Polish national platform through which B2B electronic invoices must mandatorily pass. It validates each invoice and assigns it a unique identification number.

When does electronic invoicing become mandatory in Poland?

From 1 February 2026 for large taxpayers (revenue exceeding 200 million PLN), then from 1 April 2026 for all other VAT-registered companies.

What invoice format must be used?

Invoices must be produced in structured FA format (XML), in the version applicable to KSeF 2026 flows, then transmitted to the public platform.

Does KSeF apply to invoices to individuals?

No. The mandate covers B2B transactions. There is no KSeF obligation for B2C transactions.

What is the KSeF number for?

Each invoice validated by the platform receives a unique KSeF identification number. It certifies the transmission and the legal date of issuance of the invoice, and must be kept with it.

Guide · Electronic Invoicing

Electronic invoicing in Poland: the KSeF

Poland is imposing its national KSeF platform (Krajowy System e-Faktur) for B2B invoices, with a staggered rollout in 2026: first large taxpayers, then all taxable persons.

Updated on July 31, 2026

Regulatory framework

Poland has adopted a centralized clearance model similar to Italy's: all B2B invoices must be routed through the public KSeF platform (Krajowy System e-Faktur), which assigns them a unique identification number serving as proof of issuance. Mandatory deployment will take place over the course of 2026 depending on company size.

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From February 1, 2026: obligation for large taxpayers with turnover exceeding 200 million PLN (approximately €46M).
From April 1, 2026: extension of the obligation to all other enterprises subject to VAT.
Clearance model: each invoice receives a KSeF identification number that attests to its transmission and legal date of issuance.
B2B scope: there is no obligation for B2C transactions, outside the scope of the mandate.

Formats and platforms

KSeF (Krajowy System e-Faktur): Polish public platform through which B2B invoices must be routed.

FA format (XML): structured schema imposed by the administration, in its version applicable to KSeF 2026 flows.

KSeF number: unique identifier assigned to each validated invoice, serving as proof of issuance.

Authentication: access to KSeF via certificate, authorization token or qualified signature.

Interoperability: the Polish format is part of the European framework based on the EN 16931 standard.

Archiving: retention of invoices and their KSeF number to meet tax controls.

Compliance steps

1
Find your deadline
Determine whether you fall under the February 2026 deadline (large taxpayers) or April 2026 (other VAT-taxable persons).
2
Connect to KSeF
Set up the required authentication (certificate, token or qualified signature) to send and receive via the platform.
3
Produce in FA XML format
Configure your tool to generate invoices compliant with the FA schema expected by KSeF and retrieve the identification number.
4
Archive with KSeF proof
Keep your invoices and their KSeF number in archiving with probative value to justify their legal issuance.

Frequently asked questions

What is KSeF?: KSeF (Krajowy System e-Faktur) is the Polish national platform through which B2B electronic invoices must mandatorily pass. It validates each invoice and assigns it a unique identification number.
When does electronic invoicing become mandatory in Poland?: From 1 February 2026 for large taxpayers (revenue exceeding 200 million PLN), then from 1 April 2026 for all other VAT-registered companies.
What invoice format must be used?: Invoices must be produced in structured FA format (XML), in the version applicable to KSeF 2026 flows, then transmitted to the public platform.
Does KSeF apply to invoices to individuals?: No. The mandate covers B2B transactions. There is no KSeF obligation for B2C transactions.
What is the KSeF number for?: Each invoice validated by the platform receives a unique KSeF identification number. It certifies the transmission and the legal date of issuance of the invoice, and must be kept with it.

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