KSeF 2026 – a comprehensive guide for capital and partnership companies

The National e-Invoicing System (KSeF) is a central platform managed by the Ministry of Finance for issuing, sending, receiving, and storing structured invoices in a defined XML format. The original invoice, for VAT purposes, exists only in KSeF; PDFs or printouts are merely visualizations of the data stored in the system.

Key Objectives of Introducing KSeF:

• Tightening the VAT system and reducing fraud through real-time tax authority access to invoice data.
• Automating reporting (fewer manual JPK files, easier analytics and cross-checks).
• Standardizing invoice format (single XML standard) and simplifying document flow between companies.
• Reducing costs of archiving and handling paper/PDF invoices for businesses.

For limited liability and general partnerships, KSeF represents not just a technical change but a real restructuring of financial document workflows and tax controls.

Implementation Timeline (2026–2027):

• February 1, 2026: Mandatory for “large entities” (sales exceeding PLN 200 million including VAT in 2024).
• April 1, 2026: Mandatory for all other VAT taxpayers (most SMEs, sole traders, partnerships, and companies below the threshold).
• From February 1, 2026: All VAT taxpayers must be ready to receive purchase invoices via KSeF.
• 2026: Transitional period with no administrative penalties for technical errors.
• January 1, 2027: Full enforcement of sanctions.

Who Must Use KSeF?

All VAT taxpayers (active and exempt) required to issue invoices, regardless of legal form: sole traders (JDG), limited companies (sp. z o.o., joint-stock, etc.), partnerships, foundations/associations with economic activity, and public entities issuing B2G invoices. Exclusions: private individuals not running a business and foreign entities without a Polish seat or NIP (they generally do not issue via Polish KSeF but may receive invoices).

Which Invoices Are Covered?

• Mandatory: B2B invoices (including advance, final, partial), B2G, and any invoices under Polish VAT law, including certain transactions with foreign contractors (e.g., WDT, exports, services taxed in Poland).
• B2C (to consumers): Largely optional/voluntary; businesses can still provide PDF visualizations to customers.
• Foreign contractors do not access KSeF directly; they receive invoices in agreed formats (PDF, EDI, etc.).

Structured Invoice (XML) Changes:

More mandatory fields, strict validation rules, internal invoice number retained but supplemented by a unique KSeF number. Requires review of templates, dictionaries, and system integrations.

Corrective Invoices:

Separate XML documents linked to the original via KSeF number; must specify changes and reason. VAT settlement rules remain unchanged, but tax authorities gain real-time visibility.

Registration and Authentication:

• Sole traders (JDG): Direct login via Trusted Profile or qualified electronic signature; can grant access electronically.
• Companies: Requires designating representatives (board members or authorized partners); often involves submitting ZAW-FA form to the tax office before granting further permissions.

Authentication Methods:

• Trusted Profile (mainly for individuals).
• Qualified electronic signature.
• Qualified electronic seal (especially useful for companies).
• KSeF 2.0 certificates (for system integration and offline/emergency mode).