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

Companies conducting business in Poland and the UK must prepare for two different e-invoicing regimes. Poland already operates the mandatory centralised KSeF platform, while the UK plans to require electronic issuance and receipt of all VAT invoices from April 2029. Foreign investors should establish one consistent invoice-data core supported by separate country-specific compliance processes.

How do the Polish and UK systems 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. The Polish tax administration therefore participates directly in the legal invoice-issuance process.

UK businesses may currently use paper invoices, PDF, XML or EDI. They must ensure authenticity of origin, data integrity, legibility, suitable business controls, a reliable audit trail and customer consent.

From April 2029, all UK VAT invoices are expected to be issued and received electronically. The final data standard and transmission architecture have not yet been published. Based on current plans, an ordinary PDF will not be sufficient because structured invoice data will need to pass automatically between financial systems.

When does mandatory KSeF apply?

The Polish 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 the mandatory scope;
• from 1 January 2027 for the smallest taxpayers using the temporary PLN 10,000 gross monthly threshold.

Until 31 December 2026, taxpayers remaining below this threshold may issue qualifying invoices outside KSeF. Once the limit is exceeded, the obligation applies from the invoice that causes the threshold to be breached.

Does KSeF apply to foreign investors?

A foreign company does not automatically have to issue invoices through KSeF merely because it holds a Polish VAT registration.

The key question is whether the company has:

• a place of business in Poland;
• a fixed establishment in Poland;
• personnel and technical resources participating in the transaction.

Companies with employees, offices, warehouses, infrastructure or operational teams in Poland require closer assessment. An incorrect classification may affect invoicing, VAT reporting and the broader tax position of a business in Poland.

How should Polish–UK transactions be invoiced?

A Polish supplier within the mandatory 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 supplier without a place of business or participating fixed establishment in Poland will generally remain outside the mandatory invoice-issuance scope. Each transaction should nevertheless be reviewed for VAT place of supply, registration requirements, reverse charge and reporting obligations.

How should a company investing in Poland prepare?

A single ERP connection may not satisfy the requirements in both jurisdictions. The recommended design is one invoice-data core with separate country compliance modules.

Businesses should:

• validate VAT numbers, legal names, addresses, currencies and tax rates;
• separate structured invoice data from its PDF presentation;
• ensure that systems support XML, APIs and configurable mappings;
• define procedures for rejections, offline24 and KSeF failures;
• appoint a process owner covering finance, tax, accounting and IT.

For companies investing in Poland, the immediate priority is stable KSeF compliance. UK preparations should focus on data quality and system flexibility without committing prematurely to a technical standard that has not yet been confirmed.

Read the full article here: E-invoicing in Poland and the UK: comparing KSeF with UK rules.