On 1 September 2025, an act amending the Value Added Tax (VAT) Act and introducing the mandatory National e-Invoicing System (KSeF) was published in the Journal of Laws. The new regulations represent a significant shift in the documentation of transactions for VAT purposes, affecting entrepreneurs as well as their advisers and business partners.
Under the new act, mandatory e-invoicing via KSeF will take effect as early as February 2026 for so-called large taxpayers, and from April 2026 for all others.
Although the obligation to issue e-invoices in KSeF will initially not apply to everyone, the system will nevertheless become crucial for virtually all taxpayers. This is due, among other things, to the requirement to receive and store purchase invoices, which from the indicated dates will need to be transmitted exclusively through KSeF.
In the reality of ongoing digitalisation of the tax administration, KSeF will become the central tool for verifying the circulation of invoices within enterprises, and its implementation requires proper organisational and technological preparation.
Experts at TPA Poland have prepared a bilingual publication titled “KSeF 2026: A comprehensive guide for companies. Legal basis, obligations and practical implementation” designed to support entrepreneurs as well as accounting, tax and IT professionals in understanding and practically implementing the new requirements.
In this guide, we discuss:
- The key legal foundations of KSeF,
- The implementation schedule along with a practical step-by-step guide,
- Answers to the most frequently asked questions about how KSeF works.
