Invoice outside the KSeF system. There is a problem with VAT

The new KSeF rules are starting to cause their first problems. How to settle VAT when the document reaches the KSeF with a delay or not at all.

The National e-Invoice System (KSeF) has become a fact and is starting to have a real impact on company settlements. With its implementation, the first doubts appear regarding, among others, moment of VAT deduction.

– One of the most common problems is a situation in which the buyer receives an invoice outside KSeF, and the document is only later entered into the system – notes Piotr Juszczyk, Chief Tax Advisor at inFakt.

Invoice outside the system and the moment of VAT deduction

Let’s imagine a typical scenario from the turn of March and April 2026. The entrepreneur receives a paper invoice on March 2 – without a QR code and KSeF number, i.e. a fully traditional one. Only a month later the document is entered into the system. A key question arises: when does the right to deduct VAT arise?

– In such a situation, the right to deduct input tax arises already in March, i.e. when the invoice is actually received by the buyer, provided that the other material conditions are met. The mere fact that the document was later introduced into the KSeF should not affect this right – explains Piotr Juszczyk.

As the expert emphasizes, this is also confirmed by the tax office’s interpretations. The Director of the National Tax Information pointed out that the mere issuance of an invoice outside the KSeF does not deprive the right to deduct VAT.

– In such a case, the taxpayer includes the invoice in the VAT records for March and marks it in the JPK file as an invoice outside the KSeF. During the transitional period, this will be the appropriate designation for documents issued outside the system, i.e. BFK, explains the tax expert.

Seller’s error and buyer’s obligations

The situation is different when the seller was already obliged to use KSeF, but nevertheless issued an invoice outside the system and forwarded it to the contractor.

– If such an invoice was actually received by the buyer, the right to deduct VAT also arises at that moment, for example in April. In the JPK records, such an invoice should be marked as a document issued contrary to the KSeF obligation, i.e. the DI tag – explains Juszczyk.

Here, there may be a need to organize the documentation later.

– In practice, this means correcting the JPK file for the period of the original deduction and replacing the invoice markings other than KSeF with the KSeF number. However, the moment of tax deduction does not change – it remains related to the actual receipt of the invoice – says an expert from inFakt.

Offline mode and the meaning of the KSeF number

An even different situation should be treated when an invoice was issued outside KSeF in offline mode and then transferred to the system in accordance with the regulations – usually on the next business day.

– In such a case, the moment of receipt of the invoice for VAT purposes will be the moment of assigning the KSeF number. Only then does the buyer gain the right to deduct input tax, explains Juszczyk.

This distinction is crucial for entrepreneurs:

if the invoice operates outside KSeF and reaches the system with a delay – the moment of its receipt is important,
if it is part of the standard KSeF process – the moment of assigning the number in the system is decisive.