Issuing Invoices – Deadlines in the National e-Invoicing System (KSeF)

Paweł Gorzelec
Oct 31
2 min read

The introduction of the National e-Invoicing System (KSeF) slightly reshapes the rules regarding invoice issuance deadlines. While the general principles remain unchanged, the legal meaning of the “issue date” has evolved significantly.

When is an invoice considered issued?

Under the new regulations, an invoice is considered issued on the date it is sent to KSeF. This means that until the invoice is transmitted to the system, it does not legally exist. Generating the document in accounting software is not enough.

The Ministry of Finance clarified that the document can be sent the following day, as long as it meets the statutory deadline (typically by the 15th of the month following the supply or service).

For practical safety, it’s recommended to send invoices no later than one day after the issue date.

Offline24 invoices

Taxpayers may issue structured invoices offline, following the official KSeF format, in case of temporary technical issues (e.g., no internet connection).Such invoices must be sent to KSeF no later than the next working day, to receive their unique identification number (KSeF ID).

Date discrepancies

Minor differences between the issue date indicated on the invoice and the date recorded in KSeF do not result in rejection. As long as statutory deadlines are respected, the invoice remains valid.