The implementation of the mandatory National e-Invoicing System (KSeF) involves not only the need to adapt IT systems, but also the risk of errors occurring during their implementation. In an individual tax ruling issued on 23 June 2026, ref. no. 0114-KDIP1-3.4012.298.2026.1.KP, the Director of the National Tax Information (KIS) addressed the consequences of accidentally submitting invoices to KSeF that had previously been correctly issued outside the system. The ruling also indicates what actions a taxpayer should take in such a situation.
The case concerned a taxpayer conducting business activity involving the sale of goods and registered as an active VAT taxpayer. In preparation for mandatory use of KSeF from 1 April 2026, the taxpayer was implementing an integration between its financial and accounting system and the National e-Invoicing System. During tests carried out on 24 March 2026, a technical error resulted in 2,568 invoices issued previously in February and March 2026 being accidentally submitted to KSeF.
The invoices had previously been correctly issued outside KSeF, sent electronically to contractors, recorded in VAT registers and reported in JPK_VAT files. They documented actual transactions, including both domestic sales and intra-Community supplies of goods. Their accidental submission to KSeF resulted solely from an error during integration testing and was not intended to constitute a new issuance of the documents. Nevertheless, the invoices were assigned KSeF identification numbers.
In this situation, the taxpayer asked whether the invoices accidentally submitted to KSeF could remain in the system without the need to issue corrective invoices. The taxpayer also questioned whether merely assigning KSeF identification numbers to the documents created an obligation to formally correct them and whether any corrective action was required in the circumstances.
The taxpayer argued that the accidental recording of the invoices in KSeF should not result in an obligation to correct them. It emphasised that, during the period covered by the invoices, the use of KSeF was voluntary and that all documents had been issued outside the system in accordance with the applicable regulations, delivered to contractors and correctly reported for VAT purposes. In the taxpayer’s view, the subsequent submission of the same invoices to KSeF did not result in a second sale or create a new tax obligation. It was solely the result of a technical error during integration testing, and therefore there were no grounds for issuing corrective invoices merely because the invoices had been accidentally recorded in the system.
The Director of the National Tax Information did not agree with this position. First, the authority pointed out that once an invoice is accepted by KSeF and assigned an identification number, it becomes part of legal transactions. At the same time, the applicable regulations do not provide for the possibility of deleting, cancelling or editing an invoice that has already been accepted by the system. Therefore, the accidental submission of a document to KSeF does not allow it to be simply “withdrawn” from the system.
The authority also noted that, in the case at hand, the invoices submitted to KSeF documented transactions that had already been properly documented and were already in commercial circulation outside the system. Consequently, the same transactions had effectively been documented and introduced into circulation again. According to the Director of KIS, the only way to eliminate the accidentally submitted documents is to issue corrective invoices reducing the amounts to zero.
Importantly, the authority emphasised that it was irrelevant that the incident occurred before the taxpayer became subject to the mandatory KSeF regime, as well as the fact that the documents had been submitted solely as a result of a technical error during testing. In the authority’s view, these circumstances do not change the fact that the documents were assigned KSeF identification numbers and were effectively entered into the system.
The ruling is particularly significant because it not only indicates how to deal with invoices accidentally submitted to KSeF, but also explains why, in the authority’s view, corrective action is necessary. The Director of KIS pointed out that leaving such documents in KSeF could result in the same transaction being documented by two invoices. This could, in turn, create a risk of applying Article 108 of the VAT Act, which provides for an obligation to pay VAT shown on an invoice.
The ruling therefore provides practical guidance for taxpayers. It demonstrates that even a one-off technical error made during system integration testing, resulting in historical invoices being entered into KSeF, may require corrective action. Taxpayers implementing or testing KSeF integrations should therefore pay particular attention to preventing historical documents from being accidentally transmitted to the system.