From February 1, 2026, some entrepreneurs must start issuing invoices through the National e-Invoice System (KSeF). But what do you do when the system isn't working? The Ministry of Finance has prepared three backup modes that allow you to issue invoices even when KSeF is unavailable.

In this article, we explain everything you need to know about offline mode, offline24 mode, and emergency mode.

Before we begin – it's important to understand the differences between the three modes:

Offline24 mode – you use this when you have internet problems or the network is running slowly. The system is working normally, but you can't connect to it.

Offline mode (KSeF unavailability) – you use this when the KSeF system itself is unavailable due to scheduled maintenance work. The Ministry of Finance announces this in advance.

Emergency mode – you use this when KSeF experiences a failure. The Ministry of Finance announces it in the Public Information Bulletin (BIP) and in the system.

Each of these modes has different rules and deadlines for submitting invoices to the system.

Offline24 mode – what is it and when to use it?

Offline24 mode is a solution for businesses that have problems sending invoices to KSeF. This may result from:

weak internet connection,
network problems in your location,
long wait times for invoice processing.

You can use this mode anytime – the law doesn't restrict who and when can use it.

How to issue an invoice in offline24 mode?

Prepare an electronic invoice in FA(3) structure (mandatory from February 1, 2026)
Issue the invoice normally – with the date in field P_1
Submit it to KSeF no later than the next business day after issuance

If you send the invoice the next day, it's still offline24 mode, even if you originally wanted to send it immediately.

What if a failure occurs in the meantime?

Two situations may occur:

KSeF announces a failure (in BIP and the system) – you have 7 business days from the end of the failure to submit the invoice
A total failure occurs (announced in media) – you don't submit invoices to KSeF at all

When is an invoice issued and received?

Issue date – this is the date you enter in field P_1 on the invoice. It doesn't matter when you actually submit it to the system.

Date received by the buyer:

When the buyer receives the invoice through KSeF – the date the KSeF number is assigned
When you send the invoice outside KSeF (e.g., to a consumer or foreign company) – the actual receipt date

Invoice with QR codes

If you send an offline24 invoice outside the KSeF system (e.g., by email to a consumer), you must add two QR codes:

"OFFLINE" code – allows checking the invoice in KSeF and verifying its data
"CERTIFICATE" code – confirms that you actually issued the invoice

To generate the second code, you must download a KSeF type 2 certificate.

Invoice correction in offline24 mode

You can also issue a corrective invoice in offline24 mode. Remember that:

You must also submit the correction to KSeF no later than the next business day
If you're correcting an invoice issued in offline24, first submit the original invoice to KSeF (to get a number), and only then issue the correction

Offline mode – KSeF unavailability

You use this mode when the KSeF system itself is temporarily unavailable. The Ministry of Finance announces this in advance – for example, due to scheduled maintenance work.

How to issue an invoice in offline mode?

Prepare an invoice in FA(3) structure
Issue it electronically with the appropriate date
Submit to KSeF no later than the next business day after the unavailability ends

What if a failure occurs during this time?

Similar to offline24 mode:

Normal failure – you have 7 business days from its end
Total failure – you don't submit invoices

Issue and receipt dates

The rules are the same as in offline24:

Issue date – what you enter in field P_1
Receipt date – the date the KSeF number is assigned (or actual receipt date when sending outside the system)

QR codes and corrective invoices

The rules are identical to offline24 mode.

Emergency mode – what to do when KSeF really isn't working?

You activate emergency mode only when the Ministry of Finance officially announces a KSeF failure. The information will appear:

in the Ministry of Finance's Public Information Bulletin (BIP),
in the invoice issuance application (interface software).

How to issue an invoice in emergency mode?

Issue an electronic invoice in FA(3) structure
Send it to the buyer in an agreed manner (e.g., by email)
Submit to KSeF within 7 business days from the end of the failure

What if the failure extends?

Another failure – the 7-day deadline is counted from the end of the last failure
Total failure – you don't submit invoices to the system at all

Invoice issue and receipt dates

Issue date – the date in field P_1 on the invoice

Date received by the buyer:

The actual date the buyer received the invoice
The date the KSeF number is assigned – if the buyer received the invoice later than the system assigned the number

Exception: when you send an invoice to a foreign entity, consumer, or buyer without a tax ID, the actual receipt date always counts.

QR codes in emergency mode

The rules are the same – you need two QR codes on an invoice sent outside the system.

Transaction confirmation

If the buyer is a Polish entrepreneur with a tax ID, you can additionally issue them a "transaction confirmation" – a document confirming that the transaction took place.

Invoice correction in emergency mode

You can also issue a correction in emergency mode. Just remember that you issue a correction of an emergency mode invoice only after the original invoice receives a KSeF number.

Summary – which situation, which mode?

Situation	Mode	When to submit to KSeF?
You have internet problems	Offline24	Next business day
KSeF unavailable (scheduled work)	Offline	Next business day after it ends
KSeF has a failure (officially announced)	Emergency	Within 7 business days after failure
Total failure (announced in media)	Don't submit	-

Key rules – in brief

Invoice issue date is always the date in field P_1 – regardless of when you submit it to KSeF
All modes require an electronic invoice in FA(3) structure
Two QR codes – always when you send an invoice outside the system (you need a type 2 certificate)
Corrective invoices – you can issue them in all modes, but sometimes you must wait for the KSeF number of the original invoice

What's next?

The KSeF system is a major change for all companies in Poland. Fortunately, backup modes provide flexibility and security – even when something isn't working, you can issue an invoice and run your business normally.

If you have questions, check the official KSeF website at podatki.gov.pl or contact a tax advisor.

This article was created based on official information from the KSeF portal (ksef.podatki.gov.pl). The regulations come into effect on February 1, 2026.

Offline and offline24 modes in KSeF – How to issue invoices during system outages or internet problems