An invoice won't go through to KSeF (Poland's national e-invoicing system). The question that actually matters isn't "what happened" — it's whether the problem is on your side or the system's. The answer decides how long you have to send it (one business day or seven) and whether you're even allowed to use a given mode at all.
offline24 and emergency mode are two different tools for two different situations. Confusing them costs nothing today, during the grace period, but from 1 January 2027 a late submission can carry a penalty.
This article shows when each mode applies, the exact deadlines and legal basis, and what to do when offline24 suddenly becomes an emergency.
Two different problems, two different modes
The whole distinction comes down to the source of the trouble.
offline24 is your local problem — your internet dropped, the router froze, your software isn't responding, or KSeF is processing invoices slowly. KSeF itself is up; something on your end isn't. You use this mode on your own initiative, and it's available at all times, to every taxpayer.
Emergency mode is KSeF's problem — a serious failure of the government infrastructure that the Ministry of Finance officially announces in the Public Information Bulletin (BIP, the Ministry's official announcement channel) and in the interface software (the API). Until there's an MF announcement, there is formally no emergency mode — even if the system is responding slowly.
The simplest decision rule: check the KSeF status. A green status and no outage announcement mean the problem is on your side — that's offline24. An MF outage announcement means emergency mode.
offline24 emergency mode Cause your problem (internet, software, slow API) KSeF outage announced by MF Who decides you Ministry of Finance (BIP + API announcement) Legal basis Art. 106nda of the VAT Act Art. 106nf of the VAT Act Deadline to send to KSeF next business day after issuing 7 business days after the outage ends Invoice structure FA(3) XML FA(3) XML QR codes two (OFFLINE + CERTIFICATE) two (OFFLINE + CERTIFICATE) Certificate KSeF type 2 KSeF type 2 Issue date field P_1 of the structure field P_1 of the structure
The legal basis and full description of the procedures are on the Ministry of Finance page on special modes (in Polish).
Offline24 — when the problem is on your side
offline24 (Art. 106nda of the VAT Act) was designed as a business-continuity mode, not a back door around KSeF. You issue the invoice outside the system, but still in the FA(3) structure, and you send it to KSeF no later than the next business day after the issue date. The details are on the MF page on offline24 (in Polish).
A few things to keep in mind:
The issue date is the date in field P_1 of the structure — the one you enter on the invoice yourself, not the moment it reaches KSeF.
The invoice must carry two QR codes: the first (marked "OFFLINE") provides access to the invoice in KSeF and lets the data be verified; the second (marked "CERTIFICATE") confirms the issuer's identity. You can only generate the second code with a KSeF type 2 certificate.
A domestic buyer (an active or VAT-exempt taxpayer) receives the invoice through KSeF once a number is assigned — and that assignment date is their receipt date. A foreign buyer, a consumer, or an entity without a Polish tax ID (NIP) gets the invoice outside KSeF, in an agreed way. Before the invoice has a number, you can issue a domestic buyer with a NIP a transaction confirmation (potwierdzenie transakcji).
Example (illustrative): on a Friday evening, at a fuel station with a weak connection, you issue an invoice in offline24. "Next business day" means you have until Monday to send it — the weekend doesn't count. (Replace with a real scenario if you have data.)
Emergency mode — when KSeF has an outage
Emergency mode (Art. 106nf of the VAT Act) only comes into play after an official MF outage announcement in BIP and the interface software. It isn't your fault — the government infrastructure went down — which is why the law gives you much more room.
Deadline: 7 business days from the day the outage ends to send the invoices to KSeF and have numbers assigned.
The clock resets: if MF announces another outage during your 7-day window, you count from the end of the new one. So you have to track announcements until they truly stop, not just until the first "all clear."
Handing it to the buyer: you pass the invoice to the buyer outside the system, in an agreed way; their receipt date is the date of actual receipt, not the KSeF number assignment.
Corrections: you can only issue a correction to an invoice issued during the outage after the original has been sent to KSeF and given a number. The order is fixed: original → KSeF → number → correction.
The edge case: offline24 that turns into an outage
This is the scenario that's easiest to miss. You issue an invoice in offline24 on Monday and have one business day for it. But on Tuesday morning MF announces an official KSeF outage. What happens to the deadline?
It changes: an invoice issued before the outage was announced "falls into" the emergency regime, and you send it to KSeF within 7 business days of the outage ending. The practical takeaway for any business is one thing — you have to monitor KSeF availability announcements and be able to assign each invoice to the right deadline regime.
For the full picture — this isn't two modes but four, and they line up neatly by send deadline:
offline24 (Art. 106nda) → next business day after issuing
offline – unavailability (Art. 106nh) → next business day after a planned maintenance break announced by MF ends
emergency mode (Art. 106nf) → 7 business days after the outage ends
total failure (announced through mass media, e.g. a disaster or cyberattack) → you fall back to a paper or PDF invoice, without FA(3) and without QR codes, and you do not send it to KSeF later
What this changes in practice (and how not to miss the deadline)
2026 is a grace period — a late offline submission carries no administrative penalty. That changes on 1 January 2027: from then, missing the deadline can be penalized (the rules provide for up to 100% of the invoice VAT). The takeaway is simple — don't burn the whole window "because you can." Send it as soon as the system is back.
The entire operational difficulty of these modes is that the deadline depends on which mode applies, and that requires knowing the KSeF status at the time. This is exactly where the right tool takes the risk off your hands:
Biurko detects a run of failed connections to the KSeF gateway and switches issuing into offline mode, so you don't have to manually guess whether it's already an outage.
When the KSeF environment comes back, queued invoices are resubmitted automatically — without your involvement.
A separate mechanism watches the send deadline and flags for manual review any invoice approaching the end of its window or already past it, notifying you immediately. No invoice sits silently in limbo.
Both offline modes require a KSeF type 2 certificate — Biurko reminds you about its expiry ahead of time (7/3/1 days) so an outage doesn't catch you without a valid certificate.
I cover the certificate itself in a separate post: the KSeF type 2 certificate — how to get it and why. (Placeholder — swap in the final URL.)
Quick checklist
Check the KSeF status first — green status and no announcement = problem on your side = offline24
Have your KSeF type 2 certificate downloaded before you need it (without it, an offline invoice is legally just a draft)
Remember the deadlines: offline24 = next business day, outage = 7 business days after it ends
Agree a delivery channel with buyers for offline invoices (email, portal) to avoid disputes over the receipt date
Original to KSeF and its number first, only then the correction
Don't wait until the end of the window — send as soon as the system is back
Summary
offline24 vs emergency mode isn't a matter of naming — it's a matter of the deadline and who's at fault. Your problem means offline24 and one business day. An MF-side outage means emergency mode and seven business days. Everything else — the FA(3) structure, two QR codes, the type 2 certificate — is the same, so you can't tell the modes apart on the invoice itself; the difference lives in the calendar.
If you'd rather not police this by hand, try Biurko free for 14 days — it detects the outage for you, resubmits queued invoices once the system returns, and warns you before the deadline closes.
FAQ
What's the difference between KSeF offline24 and emergency mode? You use offline24 when the problem is on your side (no internet, a software failure) — you then have until the next business day to send to KSeF. Emergency mode applies when the Ministry of Finance officially declares a KSeF outage in BIP — you then have 7 business days from when it ends.
How long do I have to send an invoice to KSeF in emergency mode? 7 business days, counted from the day the MF-declared outage ends. If another outage is announced in that time, you count from the end of the new one. The invoice must use the FA(3) structure and carry two QR codes.
How do I know whether it's a KSeF outage or my own problem? Check the system status and MF announcements. If KSeF is up (green status, no outage announcement), the problem is on your side — offline24 and a one-business-day deadline apply. An MF outage announcement in BIP means emergency mode and 7 business days.
Do offline24 and emergency mode require a certificate? Yes. In both modes, marking the invoice with the second QR code ("CERTIFICATE") requires a KSeF type 2 certificate, obtained in the KSeF 2.0 Taxpayer Application or via the API. Without it, you can't issue a valid invoice outside the system.
What happens if I miss the deadline for an offline invoice? In 2026, the grace period means a late submission carries no administrative penalty. From 1 January 2027, missing the deadline can be penalized (the rules provide for up to 100% of the invoice VAT). So it's best to send invoices as soon as possible, without waiting for the window to close.