On 30 June 2025, the Polish Ministry of Finance published the KSeF 2.0 API documentation and FA(3) Logical Structure. With the launch of KSeF 2.0, Poland aims to achieve full automation in tax reporting while enhancing data accuracy for both businesses and government authorities. This upgraded version of the national e-invoicing system introduces the new FA(3) logical structure and outlines essential integration processes for businesses and software providers. In this article, we explore what KSeF 2.0 entails and how it will impact the e-invoicing landscape.
What is KSeF 2.0?
Krajowy System e-Faktur (KSeF) is Poland’s central electronic invoicing system designed to ensure real-time reporting of invoices to the tax authorities. With the launch of KSeF 2.0, it becomes mandatory for all businesses in Poland starting in 2026. This means that businesses will need to use KSeF for issuing, receiving, and archiving invoices electronically.
KSeF 2.0, an upgrade from the earlier version, brings significant improvements in its structure, enabling more detailed invoicing and greater integration with Poland’s tax compliance infrastructure.
The mandatory implementation is set to begin on 1 February 2026, making it crucial for businesses to prepare for this transition to remain compliant with the tax laws.
FA(3) Logical Structure: What’s New?
The FA(3) structure is the latest version of the invoice schema that businesses must use for issuing invoices through KSeF 2.0. This new version replaces the previous FA(2) format and comes with enhancements that aim to improve data accuracy, validation, and interoperability.
Key Changes in the FA(3) Structure:
- Expanded Data Set: The FA(3) structure introduces additional fields, allowing businesses to include more detailed information on invoices. This makes the data transmitted to the tax authorities richer and more comprehensive.
- Improved Validation Rules: With more stringent validation rules, FA(3) ensures that only valid, complete invoices are submitted, thus reducing errors and compliance risks.
The full documentation for the FA(3 structure is available on the Ministry of Finance’s website, providing clear guidelines on the necessary fields, technical specifications, and validation checks.
The KSeF 2.0 API: Technical Details
The KSeF 2.0 API is the technical interface that allows businesses to integrate their invoicing systems with the central e-invoicing platform. This API is designed according to the OpenAPI standard, making it flexible and easy to integrate with various business software systems.
Key Features of the KSeF 2.0 API:
- SDK Libraries: The Ministry of Finance has provided Software Development Kits (SDK) for developers in Java and .NET, helping businesses quickly integrate their systems with KSeF.
- Integration Guides: Detailed integration guides are available, including example code for using API endpoints, which allows for smoother transitions and quicker development timelines.
- Change Logs: The documentation also highlights the key differences between KSeF 1.0 and 2.0, enabling businesses to understand what changes have been introduced and how to migrate from the older version.
The Integration Process: Key Dates
For a smooth transition to KSeF 2.0, the Polish Ministry of Finance has laid out a clear integration timeline. The following key dates outline the major milestones in the transition process:
- 30 June 2025: The official release of the KSeF 2.0 API documentation and FA(3) structure.
- 30 September 2025: The test environment (sandbox) for KSeF 2.0 will be made available for businesses to begin testing their systems.
- November 2025: A pilot version of the KSeF 2.0 user interface will be available for users to evaluate the system’s functionality.
- 1 February 2026: Mandatory implementation for businesses with higher thresholds and full mandatory implementation of KSeF 2.0 to receive e-invoices begins for all businesses.
- 1 April 2026: Small businesses with lower revenue thresholds will be required to adopt KSeF.
- 1 January 2027: Micro-entrepreneurs with lower turnover will be covered under the mandate.
In line with the Ministry’s implementation plan, Poland is taking an important step forward on the road to mandatory e-invoicing with this publication. The legislative framework for KSeF 2.0 is progressing, and the final regulations are expected to be in place by July 2025. These dates are crucial for businesses to note to ensure they meet the necessary deadlines.
Steps to Prepare for KSeF 2.0
The KSeF 2.0 implementation marks a major shift in Poland’s tax compliance landscape. Businesses must adapt to this new system to stay compliant and avoid complications in their reporting. To help businesses prepare, the Ministry of Finance has provided comprehensive documentation and resources, including API guides, integration instructions, and test environments.
Key Recommendations
- Review the KSeF 2.0 API documentation and FA (3) structure as soon as possible to familiarize yourself with the changes.
- Be ready to fully transition by 1 February 2026 to avoid any disruption in your invoicing and tax reporting processes.
By following these steps and staying up-to-date with the latest guidelines, businesses can ensure a seamless transition to KSeF 2.0 and remain compliant with Poland’s evolving tax regulations.
For further information and updates, visit the official KSeF Portal
