2026-03-18
The risk of a “double” invoice in KSeF – when XML and PDF don’t match
As the Polish National e-Invoicing System (KSeF) becomes more widely used, businesses are increasingly encountering a practical issue known as the “double document circulation.” This occurs when the structured invoice stored in KSeF (XML) differs from the PDF visualization sent to the customer, for example by email or through a customer portal.
In principle, visualization is meant only to make the data contained in the XML structure easier to read. In practice, however, the two documents are not always fully consistent. The problem becomes particularly serious when the PDF includes different amounts, additional line items, or elements that do not appear in the invoice recorded in KSeF.
For accounting departments and accounting firms, this creates a real dilemma. When two documents related to the same transaction present different information, the key question becomes which one should be used as the basis for accounting entries and payment. In practice, this may lead to operational errors—for example, when the procurement team registers the invoice received by email while the accounting team simultaneously retrieves the same invoice from KSeF. In extreme cases, this can result in the same transaction being recorded twice in financial systems, creating a risk of duplicate payment or overstated VAT deductions.
Two main causes are typically identified for such discrepancies. The first involves simplifications introduced by some invoice issuers. In practice, this is sometimes justified by technical limitations of XML files, for example when invoices contain a very large number of line items. The second relates to IT implementation issues—particularly incorrect data conversion processes that result in the PDF visualization not fully reflecting the information contained in the XML structure.
Regardless of the underlying cause, the outcome is the same: the risk of parallel document circulation increases. In practice, a single sale may end up being documented in two different ways—once as a structured invoice in KSeF and again as a PDF document circulating outside the system.
For this reason, there are growing calls for the Ministry of Finance to clarify the rules. Clear guidance on the relationship between
a structured invoice and its visualization could reduce uncertainty for businesses and accounting teams and prevent situations in which two different versions of the same document circulate simultaneously in the market.
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