What is KSeF? Everything About Poland's National e-Invoice System

KSeF (Krajowy System e-Faktur), or the National e-Invoice System, is a centralised IT platform operated by Poland's Ministry of Finance for issuing, storing, and sharing structured invoices. It represents the biggest invoicing reform in Poland since the introduction of JPK (Standard Audit Files). Instead of paper or PDF invoices, all documents take the form of XML files processed and archived by the government's central platform.

How Does KSeF Work?

The Invoice Issuing Process

Issuing an invoice through KSeF follows these steps:

  1. Data preparation — the entrepreneur (or their accounting software) creates an invoice in the XML format compliant with the FA(2) schema.
  2. Submission to KSeF — the XML file is sent to the system via an API (application programming interface) or the Ministry of Finance's web portal.
  3. Validation — the system checks the XML structure and data for correctness. If the invoice contains errors, it is rejected with a message explaining the reason.
  4. KSeF number assignment — after successful validation, the invoice receives a unique KSeF identification number that unambiguously identifies the document within the system.
  5. Delivery to the recipient — the counterparty gains access to the invoice in KSeF. The invoice is considered delivered the moment the KSeF number is assigned.

The KSeF Number

Every invoice issued through the system receives a unique identification number containing the date, the issuer's NIP (tax ID), and a sequential number. The KSeF number does not replace the invoice number assigned by the entrepreneur — both numbering systems operate in parallel. However, the KSeF number is required for split payment transactions and in communication with the tax office.

Authorisation and Access

Accessing KSeF requires authentication. Entrepreneurs can use:

  • Profil Zaufany (Trusted Profile) — the most popular method for sole traders
  • Qualified electronic signature — required for companies
  • Authorisation token — generated within the system, used for automated API integrations
  • Electronic seal — for legal entities

You can also grant permissions to employees, accounting firms, or IT systems.

KSeF Rollout Timeline

February 2026 — Large Enterprises

From 1 February 2026, KSeF becomes mandatory for active VAT taxpayers whose revenue in the previous tax year exceeded 200 million PLN. These entities must issue structured invoices through KSeF for domestic B2B transactions.

April 2026 — All Remaining VAT Taxpayers

From 1 April 2026, the KSeF obligation extends to all remaining active VAT taxpayers, regardless of turnover. This includes sole traders, small companies, and all entities registered as active VAT taxpayers.

Exceptions and Exclusions

Not all invoices need to pass through KSeF. Exceptions include:

  • Consumer invoices (B2C) — invoices issued to individuals who do not run a business are not required to go through KSeF
  • Invoices for foreign counterparties — international transactions (intra-Community supply, exports, import of services) are excluded from the KSeF obligation
  • Tickets treated as invoices — e.g., bus, train, and motorway tickets
  • Invoices issued in offline mode — if the KSeF system is down or the entrepreneur has no internet access, the invoice can be issued outside the system and uploaded to KSeF within 7 days of the obstacle being removed

Low-Value Threshold

For low-value transactions (up to 450 PLN gross or 100 EUR), simplified invoices are permitted. These must also be submitted to KSeF but have a simplified data structure.

How to Prepare for KSeF

1. Check Your Accounting Software

Contact your accounting software provider and make sure it supports KSeF. Most popular programmes (e.g., Symfonia, Optima, wFirma, iFirma) already have or are implementing KSeF integration. If you use an accounting firm, ask about their readiness — professional firms like LinTax Wroclaw prepared for KSeF handling during the testing phase.

2. Obtain System Access

Register on the Ministry of Finance's KSeF platform. Test the login process and grant permissions to the people who will be issuing invoices in your company.

3. Adapt Internal Processes

  • Train staff responsible for invoicing
  • Update your document workflow — KSeF invoices are available instantly, there is no need to send them by email
  • Agree with counterparties on how to identify invoices (KSeF number vs your own number)
  • Prepare a contingency procedure for system downtime

4. Test Invoice Issuing

Use the KSeF test environment to issue sample invoices. Verify that data transfers correctly from your system to the XML format.

5. Verify Your Registry Data

Make sure your details in CEIDG or KRS are up to date and your NIP is correctly verified on the VAT taxpayer White List.

Penalties and Sanctions

Failure to comply with the KSeF obligation carries financial penalties:

  • Issuing an invoice outside KSeF (once the obligation is in effect) — a penalty of up to 100% of the VAT shown on the invoice, with a minimum of 1,000 PLN
  • Late submission of an offline invoice — the same penalty, calculated from the day the 7-day deadline expires

During the first months of the system's operation (through the end of 2026), the Ministry of Finance has announced a lenient approach to imposing penalties, giving entrepreneurs time to adapt.

Benefits of KSeF

Although implementing KSeF requires effort, the system brings tangible advantages:

  • Faster VAT refunds — for invoices issued in KSeF, the VAT refund period shortens from 60 to 40 days
  • Elimination of fake invoices — the central repository makes it harder to issue fictitious invoices
  • Archiving — invoices in KSeF are stored for 10 years, so you do not need to archive them yourself
  • Automation — API integration allows full automation of the invoice workflow
  • No need to send invoices — the counterparty has immediate access to the invoice in the system

Summary

KSeF is a fundamental change in Poland's invoicing landscape. The obligation to use the system is being introduced in stages: from February 2026 for large companies, and from April 2026 for all VAT taxpayers. Early preparation is key — update your software, train your team, and test the system well in advance.

If you need help implementing KSeF or have questions about the new obligations, contact LinTax accounting firm. You can also use our tax calculators to work out your VAT liabilities, and check the latest KSeF news on our portal. For more on VAT itself, see the article What is VAT?.