E-invoicing in Poland and the UK: comparing KSeF with UK rules

E-invoicing in Poland and the UK currently follows different models. Poland has operated a mandatory, centralised KSeF system since 2026, while the UK plans to require electronic issuance and receipt of all VAT invoices from April 2029. International groups should use one invoice-data core with separate country compliance modules.

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How do e-invoicing rules differ?

In Poland, an invoice within the mandatory scope must be submitted to the National e-Invoicing System (KSeF). Once accepted, it receives a unique KSeF number and an official confirmation, so the tax administration participates directly in the legal invoice-issuance process.

In the UK, e-invoicing is generally optional. Businesses may use PDF, XML or EDI if they ensure authenticity, data integrity, legibility, business controls and customer consent.

From April 2029, all UK VAT invoices are expected to be issued and received electronically. The final data standard and transmission model have not yet been published. A standard PDF is unlikely to qualify because the future regime is intended to exchange structured data automatically.

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Who must use KSeF in Poland?

The rollout was divided into stages:

• from 1 February 2026 for taxpayers whose gross sales exceeded PLN 200 million in 2024;
• from 1 April 2026 for other taxpayers within scope;
• from 1 January 2027 for the smallest taxpayers using the temporary PLN 10,000 gross monthly threshold in 2026.

Until the end of 2026, taxpayers below that threshold may issue invoices outside KSeF. Once exceeded, the obligation applies from the invoice causing the breach.

KSeF mainly covers taxpayers with a place of business in Poland or a fixed establishment in Poland that participates in the transaction. A Polish VAT registration or tax number alone does not automatically create an obligation to issue invoices through KSeF.

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How should Polish–UK transactions be invoiced?

A Polish supplier within scope must first issue the invoice through KSeF. It may then provide the UK customer with a readable visualisation, such as a PDF containing the required QR code. The customer does not need standard KSeF access.

A UK company without a place of business or participating fixed establishment in Poland will generally remain outside scope. Further analysis is needed if local employees, an office, warehouse or team participate in sales or services.

Each transaction must also be reviewed for place of supply, VAT registration, reverse charge and reporting.

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How should systems and processes be prepared?

The recommended model is one invoice-data core with separate country modules. Businesses should:

• validate VAT numbers, legal names, addresses, tax rates, currencies and cross-border indicators;
• separate structured invoice data from PDF presentation;
• ensure the ERP supports XML, APIs and configurable mappings;
• define procedures for rejections, offline24, system unavailability and failures;
• appoint a process owner covering finance, tax, accounting and IT.

In Poland, the priority is stable KSeF compliance. In the UK, businesses should improve data and system flexibility without committing to an unconfirmed standard.

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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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