KSeF outage – offline mode and the emergency procedure

KSeF (the national e-invoicing system) is critical infrastructure – and like any infrastructure, it can fail. The VAT Act provides for this scenario: offline mode lets you issue an invoice even when the system of the Ministry of Finance (MF) does not respond, and then send it to KSeF within the deadline.

This article explains when you can use offline mode, how to issue an invoice correctly in that mode, how to send it to KSeF afterwards and what the deadlines are.

When you may use offline mode

The act distinguishes four situations. Each has a different deadline, so it is worth telling them apart.

1. Offline24 mode – always, without any outage. You can issue an electronic invoice using the template and send it to KSeF by the next working day at the latest (Article 106nda(1)–(2) of the VAT Act). The date of issue is the date on the invoice (paragraph 10). The buyer receives the invoice on the day the KSeF number is assigned (paragraph 11). An invoice delivered outside KSeF is marked with two QR codes, including the code from the KSeF certificate (paragraphs 6–7).
2. KSeF unavailability announced by the MF – invoices are sent by the next working day after it ends at the latest (Article 106nh(1)–(2)).
3. An outage announced by a notice – the deadline is 7 working days from the end date of the outage given in the notice (Article 106nf(4)).
4. A total failure (Article 106ne(3)) – invoices are not sent (Article 106nha point 2).

How to recognise an outage

Several signs that something is wrong:

• Notices of KSeF outages and unavailability are published by the Minister of Finance in the Public Information Bulletin of the MF and in the KSeF interface software; a total failure is announced in the mass media.
• Your invoicing program returns an error – instead of a KSeF number you get a connection error message
• No new purchase invoices for several hours – if you normally see new invoices from your suppliers every day and suddenly there is “silence”, there may be an outage

If you are not sure whether it is an outage or an error in your program, check in the KSeF portal directly. If the portal itself does not respond, the problem is on the MF’s side.

How to issue an invoice in offline mode

Step 1 – generate the invoice in your program

You work as usual. The program generates the invoice with full details (buyer, line items, amounts, date of issue). It does not send it to KSeF, because the system does not respond or because you deliberately choose offline24 mode.

Step 2 – assign the invoice number

You give the invoice the next number in your sequence (for example, FV/2026/04/123) and mark it in the program as issued in offline mode.

Step 3 – give the invoice to the customer with the QR codes

You deliver the invoice to the customer outside KSeF – a PDF by email, a paper printout, whatever works in your industry. Such an invoice must carry two QR codes, including the code from the KSeF certificate (Article 106nda(6)–(7)).

Step 4 – save the XML file for sending

The program saves the invoice’s XML file in the queue waiting to be sent. When KSeF is restored, it will send the pending invoices automatically. Some programs require you to click “Send pending” manually.

What exactly an offline invoice must contain

An invoice in offline mode must contain the same data as a normal KSeF invoice, plus:

• Two QR codes – including the code from the KSeF certificate; an invoice delivered outside KSeF must be marked with them
• Date of issue – the date on the invoice, that is, the actual date when you issued it (not the date it was sent to KSeF)
• Invoice number – your own sequential number FV/2026/…, which stays in place after the KSeF number is assigned
• All mandatory fields of the FA(3) structure – exactly as in a normal invoice

The invoice looks practically the same as an online one. The difference is in the time it is sent to KSeF and in the QR codes.

Sending the invoice to KSeF after an outage

When KSeF is restored, you send the pending invoices within the deadline that applies to your situation (see above):

1. You log in to the KSeF panel or start your invoicing program
2. The program sends the queue of pending XML files to KSeF (automatically or manually)
3. KSeF checks each invoice and assigns it a KSeF number
4. The KSeF number is an additional identifying number. It does not replace the invoice number you assigned (the invoice has both)
5. For the buyer, the invoice is received on the day the KSeF number is assigned

If an invoice has errors (wrong NIP tax identification number, mismatched amounts), it is rejected. Correct it and send it again, keeping an eye on the deadline.

Corrections to invoices issued offline

A corrective invoice for an invoice issued offline is not issued until the original invoice has received a KSeF number (Article 106nda(12)).

What next

Offline mode is an important part of preparing for KSeF – it is worth practising it before a real outage happens. You can stay with your own invoicing program; we help with the KSeF implementation and watch the deadlines for you. See our KSeF service or get in touch with us. If you are only starting with KSeF, begin with KSeF for beginners and the article on your first KSeF invoice.

Sources: ksef.podatki.gov.pl, podatki.gov.pl, VAT Act, Articles 106nda, 106ne, 106nf, 106nh, 106nha.