The situation that entrepreneurs will find themselves in after the mandatory National e-Invoice System comes into force will be unenviable. As Kajetan Kubicz, attorney and partner at LTCA, explains, from February 2026, a full spectrum of documentation may be in circulation, from invoices issued in KSeF to traditional, electronic or even paper invoices. The expert admits that companies may have problems recognizing which invoice to pay. Especially since in KSeF it is enough to provide the buyer's NIP and you can send a structured invoice. — If the system assigns such an invoice a KSeF number (KSeF ID), it will mean that the buyer has received it, even if the seller sent it to a different buyer than he should or if the issuer is a fraudster – warns Kajetan Kubicz.
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What invoices will be in circulation in 2026?
The expert indicates that from February 1, 2026, entrepreneurs will receive:
— from the largest entities (e.g. from the media or telecommunications supplier industry) invoices in KSeF,
— from other entities (which did not exceed the gross sales limit of PLN 200 million in 2024) invoices both within and outside KSeFas it is now, i.e. in electronic or paper version.
From April 1, 2026, smaller entrepreneurs will have to issue invoices in KSeF, but the smallest taxpayers (the so-called “digitally excluded”, whose revenues do not exceed the threshold of PLN 10,000 gross) will still be able to issue documents in electronic or paper versions. – It will remain like this until the end of 2026 – adds Kajetan Kubicz.
Moreover, in the event of a failure of the KSeF system, taxpayers will also be able to issue invoices outside the KSeF system in a manner agreed with the buyer.
Read also: What if there is a failure at KSeF or the electricity is turned off? There will be special modes of operation
What problems does this raise, especially for buyers?
— The receipt of an e-invoice at KSeF will be determined by the mere fact of indicating the buyer's NIP (Tax Identification Number) on the invoice. This means that the only entity that will decide who receives the e-invoice in KSeF will be its issuer – explains Kajetan Kubicz. The exhibitors – adds the expert – may, of course, include contractors, but also companies that simply made a mistake when providing their Tax Identification Number and fraudsters who are counting on chaos and the company to pay the invoice.
How do you go about recognizing which invoice needs to be paid?
— Different textures and several forms can create a mess. Therefore, in my opinion, after the entry into force of the KSeF the value of ongoing contacts with contractors and due diligence, as well as software that will link the invoice with a specific order or contract will increase significantly – advises Kajetan Kubicz. This way, the company will be able to recognize which purchase invoice it should pay and which it should not.
— Companies must control the status and verification of contractors on their own. The white list of taxpayers will not help with this. There will be no information there that someone must work in KSeF, or that anyone is excluded from this obligation permanently or temporarily – adds Kajetan Kubicz.
The expert emphasizes that in 2026, each invoice received by an entrepreneur outside the KSeF system should be subject to in-depth verification and increased vigilance.
— The main point is not to pay for the same expense (documented with two invoices issued in KSeF and outside KSeF) twice and to avoid double settlement of a given document (once as received, e.g. by e-mail, and once as imported from KSeF) – says Kajetan Kubicz.
How to recognize whether an invoice needs to be paid
Basically, the expert advises that companies follow three steps. In the first step, they should determine for whom the invoice was issued (whether it is intended for us), in the second step, whether it was issued incorrectly, and in the third step, what are the possible reasons for its incorrect issuance.
— If the invoice comes from a contractor with whom the company (buyer) cooperates and is intended for it, but was issued outside KSeF, we should first determine whether the contractor had the right to do soi.e. whether it operates as an entity excluded from KSeF or whether it operates with a temporary right to invoice under the old rules (e.g. as a digitally excluded entity) – explains Kajetan Kubicz.
It may happen that among the company's contractors there is one who incorrectly defines his rights or directly declares that he did not have time to complete the implementation. — It is worth recalling here that on the one hand an invoice issued contrary to the obligation outside the KSeF system still meets the definition of an invoice and has evidential value, and should therefore be subject to payment, and on the other hand, the exercise of the right to deduct VAT by the buyer may be questioned by the tax authorities – says Kubicz. In his opinion, whether the buyer will defend the right to deduct VAT from such a document will depend only on due diligence. For example, you should request an additional statement from the contractor who issued the invoice outside KSeF. — I would consider it risky to settle an invoice received outside KSeF without making any arrangements and receiving appropriate declarations from the contractor. However, if we take appropriate action and the contractor's statements are objectively reliable, including (possibly) supported by additional documents, the settlement should not be questioned – says Kajetan Kubicz.
Author: Łukasz Zalewski, journalist of the Law section of Business Insider Polska
