First weeks of taxpayers with KSeF

After the first weeks of mandatory KSeF operation for almost all taxpayers, it’s clear that the system’s operational reality has confirmed many of the concerns raised by businesses even before its implementation. To the surprise of many, the system is stable, and contrary to earlier predictions, there have been no outages that could have paralyzed company invoicing processes. However, this doesn’t mean that daily use of KSeF remains problem-free. Practice has revealed numerous interpretative and technical challenges that require further clarification.

The Ministry of Finance recently published a new question and answer (Q&A) section on the KSeF website – “KSeF in Practice.” The explanations are divided into the following categories:

1. Issuing and receiving invoices,
2. Rules of application of KSeF and legal provisions,
3. Offline mode and QR codes,
4. IT solutions, integrations and KSeF structure,
5. Permissions and authorization,
6. Technical issues.

In today’s post, we would like to present selected responses from the Ministry of Finance and discuss the latest reports from the ministry regarding the problems taxpayers face on a daily basis in connection with the use of the KSeF.

In the category “Issuing and receiving invoices” it is worth paying attention to the Ministry’s answer to question no. 13:

Question : During the transition period, when I receive a paper invoice (purchase), how can I determine whether it should be issued in the KSeF? What if a customer provides us with a paper invoice one month, only to discover the next month that they actually sent it to the KSeF (e.g., they realized they were required to do so or exceeded the PLN 10,000 limit)? Is a VAT correction necessary in this case?

Ministry of Finance’s response : Taxpayers are required to receive invoices in the KSeF system from February 1, 2026. Receiving invoices using the KSeF system has been mandatory since February 1, 2026 (except in cases exempted by law, where the invoice is submitted in an agreed-upon manner). However, if the invoice issuer uses statutory exemptions during the transition period and issues paper invoices, the buyer accepts such an invoice and retains the right to deduct the resulting tax. Re-issuing such an invoice in the KSeF system generates the seller’s obligation to pay the resulting tax. A re-issued invoice in the KSeF system should be corrected to zero. From 2027, issuing an invoice outside the KSeF system despite this obligation will result in a fine of up to 100% of the tax amount shown on the invoice.

CLDP Comment: In our opinion, the Ministry’s response is an example of a discrepancy between the approach presented by the Ministry of Finance in its explanations and the position presented by the Director of the National Tax Information System (KIS) in individual tax rulings regarding the right to deduct invoices issued outside the KSeF and then submitted to the KSeF. The previous interpretation held that an invoice first issued outside the KSeF and then entered into the system (while maintaining the identity of the transaction and data) constitutes two copies of the same document, whereas the Ministry’s response cited above indicates that an invoice submitted to the KSEF in such circumstances should be treated as a separate, empty invoice.

In the category “KSeF rules of validity and legal provisions” it is worth paying attention to question no. 16:

Question : When issuing an invoice for an internal transfer of goods, should the company also submit it to KSeF?

Ministry of Finance’s response : As of January 1, 2014, internal invoices are no longer legal. Only an internal document can be issued, and these documents are not issued by the KSeF or submitted to the KSeF.

CLDP Comment : The Ministry of Finance’s response misses the point because it confuses the movement of own goods (ICS) with internal invoices. However, the issue is the obligation to issue a standard invoice for ICS of own goods (Article 106b, Section 1, Item 3 of the VAT Act). According to somewhat controversial interpretations, such an invoice should be issued and submitted to the National Tax Administration (KSeF), so the Ministry’s response is misleading rather than clarifying.

It is also worth considering question number 12:

Question: Taxpayer A, who is obligated to issue structured invoices from February 1, 2026, has entered into a self-billing agreement with Taxpayer B, who is obligated to issue structured invoices from April 1, 2026. Should the invoice be issued in the National Taxpayer Securities and Exchange Office (KSeF)? The parties to the transaction have their registered office in Poland and use a Polish Tax Identification Number (NIP).

Ministry of Finance’s response : Yes, the obligation to issue an invoice has been in force since February 1, 2026. In this case, the key factor is the value of sales achieved by seller A, on whose behalf the buyer issues the invoice. Seller – taxpayer A – is subject to mandatory KSeF from February 1, 2026, so the self-invoicing buyer (taxpayer B) must issue invoices on his behalf under self-invoicing from February 1, 2026, even though his own sales value did not exceed PLN 200 million in 2024. Of course, taxpayer B can also voluntarily issue “his” invoices in KSeF from February 1.

CLDP commentary : Although the Ministry of Finance’s response is consistent with the literal wording of the regulations and the individual interpretations issued, which also indicate that in the case of self-billing, the seller’s turnover should be taken into account (for example, the individual interpretation of February 13, 2026, 0112-KDIL1-1.4012.872.2025.2.WK), it nevertheless touches on one of the most controversial issues under the KSeF.

Unofficial sources indicate that the issue of self-billing is to be further clarified in the KSeF manual due to the individual tax ruling issued by the Director of the National Tax Information System (KIS) on February 27, 2026, 0112-KDIL1-3.4012.874.2025.2.KK, which sparked considerable controversy and is widely commented on by tax law practitioners as being unsupported by the provisions of the VAT Act. In this ruling, the Director of the KIS rigorously defined the rules for accepting invoices under the KSeF self-billing procedure. The authority stated that the buyer should generate an XML invoice and present it to the seller for approval before submitting it to the KSeF. This position was met with considerable disapproval from businesses due to the significant logistical and procedural difficulties that would be associated with implementing the approach presented by the tax authorities.

According to reports from the Ministry of Finance, this interpretation is being reviewed, and we can expect a response from the Ministry soon. This is definitely good news, as the more details are provided in the manual, the fewer (or at least we hope so) doubts will remain regarding the practical application of the KSeF.

Unfortunately, however, the Ministry is slow to provide clarification on all questionable issues. For example, we would like to draw your attention to a problem that has arisen during the practical application of the KSeF – tax offices require the submission of the ZAP-3 form as a condition for granting access to the KSeF, even though the regulations do not explicitly provide for it. In this regard, identifying the person in the ZAW-FA should be sufficient. Consequently, taxpayers have begun to ask the Ministry of Finance whether such an additional requirement has a legal basis.

The problem, however, is that the Ministry does not provide a clear answer. Instead of unequivocally confirming or denying the obligation to submit ZAP-3, the Ministry consistently avoids addressing this issue directly. As a result, uncertainty remains regarding the next issue.

The situation is similar when it comes to visualizing export invoices issued to foreign customers, particularly regarding the possibility of including additional customs information. Instead of providing a clear stance, the Ministry merely indicates that it is reviewing the issue and considering the appropriateness of such a solution.

Summary

Although the KSeF is technically stable, its practical application still raises many doubts. Explanatory notes published by the Ministry of Finance do not always resolve all issues, and new questions arise constantly.
It is hoped that with time and developments in practice and interpretation, the number of ambiguities will gradually decrease.