E-invoices in KSeF – New FA(3) logical structure from 1 February 2026. What will change?

Starting from 1 February 2026, a new logical structure for e-invoices – FA(3) – will come into force in Poland. It will replace the current FA(2) format used in the National e-Invoicing System (KSeF). The Polish Ministry of Finance has already released a draft version of the new schema, with final publication scheduled for June 2025.

What does this mean in practice, and how should businesses and accounting firms prepare?

What is the FA(3) Logical Structure?

The logical structure defines the technical “skeleton” of a structured invoice (e-invoice), specifying how invoice data must be presented in an XML format compliant with KSeF.

From 1 February 2026, every e-invoice issued and transmitted via KSeF will be required to follow the FA(3) schema – including original, corrective, and settlement invoices – even if they refer to transactions from earlier periods.

Key changes in the FA(3) e-invoice structure

The new FA(3) version was developed in response to feedback from Polish businesses, accountants, auditors, and software providers.

Key updates include:

• Attachments can now be added to e-invoices – such as specifications, contracts, or delivery protocols.
• New contractor type: employee – allowing easier handling of business expense reimbursements.
• Address field is no longer mandatory for some entities (e.g. third parties), simplifying invoice creation.
• The number of items per batch correction has been limited to 50,000 – previously there was no limit.
• Bank account number format has been updated – longer formats and special characters are now allowed.
• Expanded date range – dates as early as 1990 can now be used (e.g. for contract or order dates).
• Tax ID field adjusted – now allows special characters.
• Special identifiers for local government entities (JST) and VAT groups – making these easier to identify in the system.
• Increased character limit for the product/service name field – up to 512 characters for more detailed descriptions.
• Improved partial payment indicator – enabling specification of multiple payments covering one invoice.
• New field for payment link – making it easier for customers to pay invoices online.
• New field for KSeF payment identifier – helping to match payments with specific invoices more efficiently.

Better integration and future compatibility

• FA(3) is more integration-friendly with accounting and ERP systems.
• It brings the Polish KSeF system closer to European standards, although it still does not fully align with EN 16931, the EU-wide e-invoicing norm.

Timeline and compliance obligations

The transition from FA(2) to FA(3) will take effect on 1 February 2026. From that point:

• All taxpayers issuing invoices via KSeF will be required to use the FA(3) format.
• Large enterprises (annual turnover above PLN 200 million) must be ready by February 2026.
• All other taxpayers will need to comply from 1 April 2026.
• As of 1 January 2027, further integration is planned – including mandatory links between KSeF and fiscal cash registers.

What does this mean for businesses?

The transition to FA(3) is more than a technical update – it also has significant organizational implications.

Companies must:

• Update their accounting software.
• Integrate new fields into their payment and invoicing processes.
• Test the new invoice structure within their ERP systems.
• Train accounting and finance teams on the changes.
• Accounting firms should also verify that their systems will support FA(3) and assess the impact on automation and reporting workflows.

Why it’s best not to wait

Although penalties for non-compliance with KSeF have been suspended until the end of 2026, delaying implementation may still lead to:

• invoice errors,
• payment disruptions,
• overload of internal teams as deadlines approach.

The implementation of FA(3) marks a crucial step toward the full rollout of Poland’s mandatory e-invoicing system (KSeF). With the draft schema already available and the final documentation set for publication in June 2025, businesses have a clear opportunity to prepare. Now is the right time to take action.

If you have any further questions or require additional information, please contact your business relationship person or use the enquiry form on the HLB Poland website.

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