Poland’s National e-Invoicing System (Krajowy System e-Faktur, “KSeF”) is now a core element of VAT compliance for businesses operating in Poland. For foreign companies, the key question is not simply whether they are registered for Polish VAT, but whether they are required to issue structured invoices through KSeF. This should be assessed before entering the Polish market or changing the local operating model.

Key KSeF Facts Overview

What Is KSeF and How Does E-Invoicing in Poland Work?

KSeF is an ICT system used for issuing, transmitting, receiving, accessing and storing structured invoices. It validates submitted XML files against the FA(3) logical structure and system requirements. Acceptance by KSeF does not confirm the substantive correctness of the invoice, the VAT rate, the right to deduct VAT, or the counterparty’s status.

• Structured invoice – an invoice issued through KSeF in XML format using the FA(3) logical structure, and assigned KSeF number;
• Visualisation – a human-readable presentation of invoice data (e.g. a PDF or printout); it is not a separate invoice and may need to include the required QR code or codes when used outside KSeF;
• KSeF number – a unique identifier assigned automatically after the invoice file has been accepted by KSeF;
• KSeF UPO – an official acknowledgement confirming that the invoice file has been accepted by KSeF and containing the assigned a KSeF number.

Does Every Foreign Business Have to Use KSeF in Poland?

Registering for VAT in Poland does not, by itself, trigger the obligation to issue structured invoices through KSeF. For a foreign business, the key issues are whether it has a place of establishment or a fixed establishment (FE) in Poland, and where an FE exists, whether that FE participates in the supply documented by the invoice. The assessment should therefore be made for the specific operating model and transaction.

• Place of establishment in Poland – as a rule the obligation to issue invoices through KSeF applies.
• No place of establishment, but a Polish FE participates in the supply –as a rule, KSeF applies to invoices relating to those supplies, subject to statutory exclusions.
• No place of purchestablishment and no FE in Poland – no mandatory KSeF invoicing; voluntary use of KSeF is permitted.
• A Polish FE exists but does not participate in a relevant supply –its mere existence does not automatically trigger mandatory KSeF invoicing for that supply; the position should be documented.

VAT Registration and the KSeF Obligation Are Two Separate Matters

A foreign business may be registered for VAT, file JPK_VAT and settle VAT in Poland, without being required to issue structured invoices through KSeF. VAT registration, a Polish tax identification number and JPK_VAT filings do not, by themselves, establish a Polish FE. A separate, facts-based assessment is required, focusing on the permanence of the local presence, the available human and technical resources, the level of control over those resources and their involvement in the relevant supplies.

How Does the KSeF e-invoicing Process Work?

The standard process involves preparing invoice data, creating an XML file compliant with FA(3), submitting it for technical and semantic validation, and obtaining a KSeF number and UPO. A document becomes a structured invoice only when the file is accepted and a KSeF number is assigned. If the file is rejected, no structured invoice has been issued, the error should be corrected and the file resubmitted. Once an invoice has been accepted by KSeF it cannot be edited, cancelled or deleted. Errors in an accepted invoice are corrected by issuing a corrective invoice.

Before submitting an invoice, it is advisable to verify in particular:

• the purchaser’s status and tax identifier, including the correct Polish NIP where relevant,
• the correct invoice type and dates,
• VAT rates and the taxable base,
• the data required by the FA(3) structure,
• the authorisations of the person or system submitting the file.

What Happens If KSeF Is Unavailable?

KSeF in Poland provides distinct procedures for invoices issued without a current connection to the system or during officially announced unavailability or failure:

• Offline24 – may be used without a specific statutory trigger, the invoice must be submitted promptly no later than on the next business day after the day of issue.
• Offline / KSeF unavailability – used when system unavailability has been officially announced; the invoice must be submitted no later than on the next business day after the unavailability period ends.

KSeF failure (emergency) mode – used when KSeF failure has been officially announced, the invoice must be submitted to KSeF within 7 business days after the failure ends.

Total KSeF failure – invoices are issued outside KSeF, in paper or electronic form and are not subsequently submitted to the system.

Except in the case of a total KSeF failure, invoices issued in these special modes must be prepared electronically using the FA(3) structure. If such an invoice is made available outside KSeF before it is submitted to KSeF and assigned a KSeF number, it must bear two QR codes: “OFFLINE” and “CERTYFIKAT”. Generating the second code requires a valid type 2 KSeF certificate.

Penalties and Key Risks

KSeF-specific monetary penalties apply to infringements committed from 1 January 2027. The 2026 transitional period should be used to stabilise access rights, invoice validation, special-mode procedures, receipt of purchase invoices and reconciliation with JPK_VAT. The absence of KSeF-specific monetary penalties in 2026 does not remove the need to comply with general VAT requirements.

The most common risk areas include:

• incorrect assessment of whether a Polish FE exists and whether it participates in the relevant supply,
• lack of readiness to issue and, where applicable, receive invoices in KSeF,
• an inadequate or overly broad authorisation structure,
• no procedure for rejected files, corrective invoices and purchase-invoice monitoring;
• missed special-mode submission deadlines or missing QR codes and certificates;
• incorrect classification or reporting of KSeF-related invoices and documents in JPK_VAT, including the NrKSeF field and the, OFF, BFK and DI markings.

KSeF Compliance Going Forward

Where mandatory KSeF applies, the legally relevant structured invoice is not a PDF or printout, but a set of data in the prescribed XML format that has been accepted by the system and assigned a KSeF number. For foreign businesses entering or already operating in Poland, compliance with e-invoicing in Poland should be addressed at the market-entry or business-model planning stage, this means the taxpayer’s KSeF status, access model and invoicing workflow should be addressed at the market-entry or business-model planning stage – not treated as a technical detail to solve later.

If you need guidance on assessing your KSeF obligation or fixed establishment risk, setting up access, or implementing the invoice-issuing and invoice-receipt processes, the tax team at AIDER Polska is ready to assist.

Piotr Steczyszyn

Senior Tax Manager | Tax Adviser | Lawyer

AIDER Polska