Starting in 2026, most VAT taxpayers in Poland will be required to issue structured invoices exclusively through the National e-Invoicing System (KSeF). This change will impact nearly every business, from local companies to global exporters. With these new rules, one question arises: can an invoice in KSeF be issued in a foreign language? The answer is more complex than it seems.
KSeF 2026 – what does it change in eInvoicing in Poland?
The National e-Invoicing System (KSeF) is an IT platform managed by Poland’s tax administration. From 2026, it will become mandatory for most VAT taxpayers. An invoice in KSeF is not a standard PDF document. Its core is an XML file that follows a defined logical structure. These XML data are crucial for tax settlements.
A visual representation of the invoice (a readable version for the recipient) will still be used, but it must accurately reflect the data from the XML file. Adding information that is not included in the e-invoice structure is prohibited. This is important because many businesses will want to prepare versions in foreign languages for international clients.
Does an eInvoice in KSeF have to be in Polish?
Although KSeF operates in Polish, tax regulations do not impose an obligation to issue invoices or commercial documentation in this language. The VAT Act does not contain any provision requiring the use of Polish. In practice, this means that in B2B transactions, especially with foreign contractors, using a foreign language is allowed.
When Is Polish Mandatory in KSeF?
In dealings with domestic consumers and public institutions, the Polish Language Act applies. It requires the use of Polish in documents related to product and service names, warranty conditions, consumer information, user manuals, and invoices.
This means that invoices issued to consumers residing in Poland and for public law entities must be prepared in Polish.
eInvoices in Poland for foreign contractors: what are the rules?
If the invoice recipient is a business based outside Poland and the document does not relate to a transaction for a Polish consumer, the invoice may be issued in a foreign language. There is no restriction on including product and service names in English, additional notes such as “payment terms” or “reference number,” and even a visual version in the same language.
However, remember that the visual representation must match the XML data. Adding information not included in the e-invoice structure is prohibited. This is a key requirement that will be monitored.
Tax Audit: the obligation to translate
Using a foreign language does not mean complete freedom. During an audit, the tax authority may request a translation of the invoice or other supporting documents, such as contracts or purchase orders, into Polish, in accordance with Article 287 of the Tax Ordinance. This obligation rests with the taxpayer, regardless of whether the invoice was issued in compliance with the law.
Therefore, it is wise to prepare for this scenario, for example, by using bilingual invoices.
Bilingual eInvoices in KSeF: a practical compromise
Many businesses choose bilingual invoices: in Polish and a foreign language simultaneously. This solution facilitates communication with international partners, streamlines accounting, and minimizes the risk of issues during audits.
In practice, this means adding product and service descriptions in two languages, such as “Usługa transportowa / Transport service.” This approach is particularly useful for intra-EU transactions.
If a bilingual visualization of e-invoices is needed, check whether your invoicing software supports issuing documents in a way that maintains good business relationships and smooth communication with clients.
Confirmation in a tax interpretation
The rules described above are confirmed by an individual interpretation issued by the Director of the National Tax Information on July 3, 2025 (ref. 0114-KDIP1-3.4012.333.2025.2.AMA). It deemed correct the position of a company planning to issue structured invoices in a foreign language for foreign contractors.
This is an important signal for companies operating internationally: the regulations are clear, but proper preparation is essential.
Common mistakes with foreign language invoices
Although the regulations allow flexibility, mistakes often occur that can cost time and money. The most common include missing required XML data, unclear translations, confusing invoice language with currency, or omitting the VAT number of an EU contractor.
It is worth ensuring professional translations and compliance with the VAT Act. This will prevent future problems and guarantee smooth invoice verification and timely payments.
Summary
Issuing e-invoices in foreign languages is permitted under Polish law and is often very practical. However, compliance with KSeF requirements, preparing accurate visualizations, and readiness to translate documents into Polish during audits are essential. In many cases, bilingual invoices are a safe and convenient solution.
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