Poland Releases KSeF 2.0 API & FA (3) Schema: What Businesses Must Know Before 2026

On June 30, 2025, Poland?s Ministry of Finance reached a major milestone in its e-invoicing reform: the official publication of the KSeF 2.0 API documentation and the final FA (3) e-invoice schema. This release sets the stage for the mandatory adoption of structured e-invoicing for all businesses, starting in 2026

What Is KSeF 2.0?

KSeF (Krajowy System e-Faktur) is Poland?s national e-invoicing platform, designed to streamline tax reporting, enhance compliance, and facilitate real-time oversight by tax authorities. The 2.0 upgrade introduces the FA (3) schema?a new XML standard for all e-invoices?and a modernized API, both of which are now fully documented and available for integration

What?s in the API 2.0 Documentation?

• OpenAPI 3.0.4 specification: Standardized interface for seamless integration with ERP and accounting systems.
• Interactive online documentation: Detailed descriptions of all endpoints, parameters, data schemas, response codes, and sample API calls.
• Integration guides: Step-by-step instructions for authentication, invoice submission (interactive and batch modes), and UPO (official receipt) retrieval, with code samples in Java and .NET.
• SDK libraries: Ready-to-use libraries for Java and .NET to speed up development and integration.
• Change logs: Clear summary of improvements and differences between KSeF 1.0 and 2.0.
• Sample invoice files: Example FA (3) e-invoices for testing and validation.

Key Features of KSeF 2.0 API:

• Full automation of invoice processing and real-time tax reporting.
• Broader integration thanks to OpenAPI standards, ensuring compatibility with a wide range of business software.
• Enhanced data accuracy with new fields, validation rules, and expanded VAT codes.
• Support for attachments, allowing supplementary files to be included with invoices.
• Comprehensive support materials: Informational brochures, legal framework explanations, and operational guides are available to help businesses prepare.

New Updates and Supporting Documents

In addition to the core features, the latest documentation and supporting materials now cover:

• Offline Modes: Guidance on how to handle invoice processing and submission when connectivity is temporarily unavailable, ensuring business continuity. There are four types of offline mode- Offline24, offline, failure and total failure mode. Based on the mode, several business and compliance related procedures will be decided such as use of QR codes, deadline to later send the invoice to the system, rules to make invoices available to buyers.

• QR Codes: Two types of QR codes will be provided
  QR code 1: To be used in invoices issued online on KSeF and shared outside.
  QR Code 2: It includes two QR codes-
  offline QR code to provide access to invoice in KSef and validates invoicedata,
  2.  'certyfikat' tag to confirm user?s identity. A KSeF certificate is required to issue this QR code.

• KSeF Certificates: From Jan1 2027 onwards, instead of using the customer certificate just for token generation, the KSef certificate itself will be used for every API call as an authentication and no access token will be issued.
• Comprehensive support materials: Informational brochures, legal framework explanations, and operational guides to help businesses prepare.

How Should Businesses Prepare?

• Review the official KSeF 2.0 API documentation and FA (3) schema as soon as possible.
• Begin integration and testing in the sandbox environment from September 2025.
• Update internal systems and workflows to ensure compliance by the relevant mandate date.
• Monitor legislative updates as regulations are expected to be finalized by July 2025.
• Leverage SDKs and guides provided by the Ministry to reduce development time and risk

Conclusion:
The publication of the KSeF 2.0 API and FA (3) schema marks a new era for e-invoicing in Poland. With the addition of updates and supporting documents such as offline modes, QR codes, and KSeF certificates, businesses are equipped with comprehensive resources to ensure a smooth transition ahead of the 2026 mandate. Act now to update your systems, begin testing, and ensure compliance. Contact us today for expert guidance and a seamless KSeF 2.0 integration experience.