The introduction of the National e-Invoicing System (KSeF) does not only change the way invoices are issued and circulated, but also introduces a number of amendments to the VAT Act intended to ensure the proper functioning of structured invoices.
One of the practical issues that may raise doubts is the determination of the invoice issuance date in KSeF. Is the decisive factor the date the invoice is submitted to the system, or the date indicated by the taxpayer on the invoice, i.e. in field P_1 of the logical FA structure?
This question is of significant practical importance. As a general rule, the invoice issuance date does not determine the moment when the tax obligation arises, but there are exceptions to this rule. In the case of certain transactions, such as construction services, the correct determination of the invoice issuance date may be crucial.
What you will learn from this article:
- whether KSeF has simplified the rules for determining the invoice issuance date,
- what significance field P_1 in the invoice structure has,
- when the submission date to KSeF is decisive,
- how the invoice issuance mode affects its date,
- how to determine the issuance date in the case of offline24 mode, KSeF unavailability, emergency mode, and full system failure.
Invoice issuance date – the starting point
The invoice issuance date appears to be an intuitive concept. It is the day on which the invoice is actually issued – neither earlier nor later, but the moment when the document is prepared and issued by the taxpayer. However, KSeF complicates this issue, as a structured invoice operates within a specific technical and legal environment. This means that, in addition to the date indicated on the invoice itself, the moment of submission to KSeF may also be relevant.
The starting point is Article 106e(1)(1) of the VAT Act. Under this provision, an invoice must include the date of issue. In the case of a structured invoice, this will be the date indicated in field P_1 of the logical invoice structure.
At the same time, Article 106na of the VAT Act provides that a structured invoice is deemed to be issued on the date it is submitted to the National e-Invoicing System (KSeF).
At first glance, this may therefore raise a question: if the invoice includes an issuance date in field P_1, but the law indicates the submission date to KSeF as the issuance date of a structured invoice, which date is decisive?
Online mode – submission date to KSeF
In the standard online mode, the invoice is issued by sending an XML file to KSeF. In this case, the issuance date of the structured invoice is the date of submission to KSeF.
In practice, this means that the date indicated in field P_1 should correspond to the date of submission to the system.
Therefore, if the taxpayer issues an invoice in online mode and submits it to KSeF on the same day indicated in field P_1, there should be no doubt. The invoice issuance date will be the submission date to KSeF, consistent with the date indicated in field P_1.
What if the P_1 date is earlier than the KSeF submission date? Offline24 mode
Doubts arise when the date indicated in field P_1 is earlier than the actual submission date of the invoice to KSeF. In such a situation, Article 106nda of the VAT Act applies, which regulates the offline24 mode. Under this mode, the taxpayer may issue an invoice in electronic form in accordance with the applicable logical structure and then submit it to KSeF within the prescribed timeframe.
In offline24 mode, the invoice issuance date is considered to be the date indicated by the taxpayer on the invoice, i.e. the date from field P_1.
Article 106nda(16) of the VAT Act is also relevant. It states that if the submission date of a structured invoice to KSeF is later than the date indicated on the invoice, such an invoice is considered to have been issued in offline24 mode.
This means that if the taxpayer indicates an earlier date in field P_1 and submits the invoice to KSeF later, the issuance date should not be determined solely based on the submission moment. In such a case, the decisive factor is the date indicated in field P_1, and the invoice is treated as issued in offline24 mode.
Field P_1 as a key invoice element
In practice, field P_1 therefore plays a very important role. It is in this field that the taxpayer indicates the invoice issuance date.
However, this does not mean that the submission date to KSeF is irrelevant. On the contrary – the submission date allows for determining whether the invoice was issued in online mode or whether the rules applicable to offline24 mode apply.
A practical distinction can therefore be made:
| Situation | Invoice issuance date | Practical comment |
| Invoice issued in online mode, submitted to KSeF on the date indicated in field P_1 | submission date to KSeF | In online mode, the submission date should correspond to the date indicated in field P_1. |
| Invoice issued in offline24 mode, including when submission to KSeF is later than the date indicated in field P_1 | date indicated in field P_1 | The mere later submission does not imply KSeF unavailability or system failure. If no official announcement of unavailability or failure has been issued, the invoice is treated as issued in offline24 mode. |
| Invoice issued in special modes related to KSeF operation, i.e. during system unavailability or emergency mode | date indicated in field P_1 | These modes apply only when KSeF unavailability or failure has been formally announced. |
| Invoice issued in case of full KSeF failure | date indicated by the taxpayer on the invoice | In this case, the invoice is issued outside KSeF, in paper or electronic form, so field P_1 may not always be applicable. |
KSeF unavailability
The law also provides for an offline mode related to KSeF unavailability. Under Article 106nh of the VAT Act, provisions applicable to offline24 mode apply accordingly to invoices issued in this mode.
In practice, this means that the invoice issuance date during KSeF unavailability is the date indicated by the taxpayer on the invoice, i.e. the date from field P_1.
Emergency mode
Another special mode is the emergency mode regulated in Article 106nf of the VAT Act.
In this case as well, the legislator explicitly states that the invoice issuance date is the date referred to in Article 106e(1)(1) of the VAT Act, i.e. the date indicated by the taxpayer on the invoice.
For structured invoices, this will be the date indicated in field P_1.
Full system failure
A separate case is a full KSeF failure. In such a situation, invoices are issued outside KSeF – in paper or electronic form.
In the case of a full failure, general VAT rules apply. This means that the invoice issuance date will be the date indicated by the taxpayer on the invoice.
Summary
Determining the invoice issuance date in KSeF requires consideration of the mode in which the invoice was issued. In the standard online mode, a structured invoice is deemed issued on the date of its submission to KSeF. In practice, this date should correspond to the date indicated by the taxpayer in field P_1.
However, if the submission date to KSeF is later than the date indicated in field P_1, the invoice is treated as issued in offline24 mode. In such a case, the invoice issuance date is the date indicated by the taxpayer in field P_1. The same principle applies to offline mode related to KSeF unavailability and emergency mode. In both cases, the invoice issuance date is the date indicated on the invoice, i.e. in practice the date from field P_1.
In the case of a full system failure, the taxpayer issues the invoice outside KSeF – in paper or electronic form – and the issuance date is determined according to general rules.
Consequently, field P_1 remains a key invoice element. The submission date to KSeF is primarily relevant for determining whether the invoice was issued in online mode or whether special mode rules apply.
