KSeF Outage 2026 — Offline, Offline24 & Emergency Modes Explained

What to Do When KSeF Is Down — The Short Answer

If KSeF (Krajowy System e-Faktur — Poland's mandatory e-invoicing platform) is unavailable — whether due to a system-wide outage announced by the Ministry of Finance or simply because your own internet is down — you are legally entitled to issue an invoice in one of three fallback modes. Each mode differs in the trigger event and the deadline for uploading the document to KSeF once it's back online. The critical principle: an invoice issued offline is legally valid from the moment you hand it to the buyer, not from the moment it reaches KSeF. This fundamental rule is codified in Art. 106na(3) of the VAT Act and has been in force since 1 February 2026. Below you'll find a detailed comparison of all three modes, technical requirements, and practical guidance — so you're never left without a sales document in front of a client.

Three Fallback Modes — When Does Each Apply?

Polish legislation anticipates three scenarios in which a business may lawfully issue an invoice outside the standard KSeF workflow. Each has its own legal basis and a different deadline for uploading the document. Here's the full comparison:

Feature	Offline24 Mode	Offline Mode (Announced)	Emergency Mode (Total Outage)
Trigger	Problem on the taxpayer's side (no internet, hardware failure)	KSeF unavailability announced by MF (Ministry of Finance)	Total outage announced in BIP MF (Official Public Information Bulletin)
Who initiates	The entrepreneur, on their own initiative	MF (Ministerstwo Finansów) via ksef.podatki.gov.pl	The Minister of Finance via BIP MF
Upload deadline	By the end of the next business day	Next business day after the announced downtime ends	7 business days after the outage ends
Required XML schema	FA(3)	FA(3)	FA(3)
Certificate	KSeF Type 2	KSeF Type 2	KSeF Type 2
QR code + invoice number on printout	Yes (mandatory for the buyer)	Yes	Yes
Legal basis	Art. 106nf(1) of the VAT Act	Art. 106ne(1) of the VAT Act	Art. 106ne(5) of the VAT Act

As you can see, the modes primarily differ in the upload deadline — from one business day to seven. In practice, this gives entrepreneurs flexibility proportional to the scale of the problem.

Offline24 Mode — When the Problem Is on Your End

This is the most common scenario in day-to-day operations. Picture this: it's Monday morning, a supplier is waiting for an invoice, and your router is dead. Or you're at a trade fair and your mobile hotspot refuses to cooperate. In cases like these, you use offline24 mode.

The procedure is straightforward:

1. Issue the invoice in your accounting software using the XML FA(3) schema.
2. Your system signs it with the KSeF Type 2 certificate (the offline certificate).
3. Generate a PDF or printout with the QR code and invoice number — hand it to the buyer.
4. Once your connection is restored, upload the invoice to KSeF by the next business day at the latest.

Example: "Meblokraft" Sp. z o.o. issues invoice FV/2026/05/0147 on Friday, 15 May 2026 at 14:30 (internet has been down since morning). Connectivity returns on Saturday. Upload deadline: Monday, 18 May 2026 (the next business day). The invoice amount — 47,850.00 PLN net + 11,005.50 PLN VAT — is irrelevant; the rule applies identically whether it's 100 PLN or a million.

For a walkthrough of the standard invoicing process, see our guide: How to Issue an Invoice in KSeF — Step by Step.

Offline Mode — When KSeF Itself Is Down

The second mode activates automatically when MF publishes a notice of system unavailability on ksef.podatki.gov.pl. You don't need to do anything special — your accounting software should detect the status and switch to offline mode on its own.

Upload deadline: the next business day after the downtime ends. If MF announces a break from Tuesday through Thursday, Friday is your deadline.

Important practical note: if you simultaneously have no internet (offline24 conditions) and MF has announced KSeF unavailability (offline conditions), you follow the mode with the shorter deadline. Typically that's offline24 (next business day from the date of issue), unless the MF system comes back sooner.

Emergency Mode — Total Outage Announced in BIP

This is the most serious scenario. Emergency mode is declared by the Minister of Finance in the Biuletyn Informacji Publicznej (BIP MF — Poland's official public information bulletin) when the outage is total and prolonged. Think of it as comparable to the December 2023 incident, when the entire KSeF system (then still voluntary) was down for several days.

Upload deadline for invoices issued in this mode: 7 business days from the end of the outage. This gives businesses a realistic buffer — especially firms issuing hundreds of invoices daily (wholesalers, retail chains, logistics companies).

The Cascading Mechanism

The legislature anticipated a scenario where outages repeat. If a new outage occurs during the 7-business-day upload window, the new 7-day deadline is counted from the end of the latest outage. This extension is automatic — no action required from the taxpayer.

Cascading example: Outage #1 runs from 5 to 9 May 2026. Upload deadline: 20 May (7 business days). But on 16 May, MF declares Outage #2 (lasting until 19 May). New deadline: 28 May 2026 (7 business days from 19 May). All invoices issued during both outage periods can be uploaded by 28 May.

Technical Requirements Common to All Modes

Regardless of which KSeF fallback mode you use, the technical requirements are identical:

• XML FA(3) schema — the third version of the structured invoice schema. Your software must generate documents conforming to this schema even when offline.
• KSeF Type 2 certificate — a special certificate used for signing invoices issued outside normal mode. You download it from ksef.podatki.gov.pl before an outage occurs (you cannot download it when the system is down).
• QR code + invoice number — every printout or PDF handed to the buyer must include a QR code enabling document verification and the invoice number. This is required by Art. 106gb(5) of the VAT Act.
• Local storage — until upload to KSeF, the invoice must be stored in a way that guarantees authenticity of origin and integrity of content (analogous to Art. 106m of the VAT Act).

For the full technical implementation guide, see KSeF 2026 — Complete Implementation Guide.

Which Software Supports Fallback Modes?

As of May 2026, full support for offline modes (including automatic invoice submission once KSeF is restored) is offered by:

• Comarch Optima — from version 2026.1. Automatic send queue with retry every 15 minutes.
• Symfonia — e-Faktura module. Real-time KSeF status detection.
• Fakturownia — offline mode with local cache. Automatic upload upon detecting availability.
• wFirma — full offline24 and offline support with email alerts.
• InFakt — since March 2026. Type 2 certificate integration with auto-upload.
• bramka-ksef.pl — dedicated API gateway with queuing and automatic retry.

If you use a smaller program or a custom-built solution, verify that it supports the FA(3) schema and can store invoices locally until upload. Without this capability, you'll need to upload manually — and with a high volume of documents, that creates a real risk of missing deadlines.

Mandatory KSeF Deadlines — Context for Fallback Modes

The offline modes came into effect alongside mandatory e-invoicing. If you're an expat running a business in Poland, these are the dates you need to know:

• 1 February 2026 — KSeF mandatory for large taxpayers (annual turnover above 200 million PLN)
• 1 April 2026 — KSeF mandatory for all active VAT taxpayers

This means that since 1 April 2026, every entrepreneur issuing VAT invoices must have outage procedures in place. For the full implementation timeline, see Mandatory E-Invoicing — When Does It Start in 2026?

Most Common Mistakes

• Mistake 1: Not downloading the Type 2 certificate in advance. The offline certificate must be downloaded while KSeF is operational. If you haven't done this, you won't be able to issue a compliant offline invoice when an outage hits. Download it immediately after reading this article.
• Mistake 2: Late upload. An invoice issued in offline24 mode on Friday, uploaded only on Tuesday (instead of Monday). Consequence: a penalty under Art. 106ni of the VAT Act — up to 100% of the VAT amount on the invoice. During the transitional period (through 31 December 2026), penalties are lighter but not zero.
• Mistake 3: No QR code on the buyer's printout. An offline invoice without a QR code is technically non-compliant — the buyer cannot verify its authenticity. Tax offices may treat it as if no invoice was issued at all.
• Mistake 4: Using offline24 mode without a legitimate reason. If your internet works and KSeF is operational, issuing in offline24 mode "for convenience" constitutes abuse. An audit may challenge your right to use this mode and impose a sanction.
• Mistake 5: Outdated software. Older versions of Comarch, Symfonia, or InFakt may not support the FA(3) schema or Type 2 certificate. Update your software before relying on fallback modes.

Step-by-Step Procedure — Universal Outage Protocol

1. Identify the cause — is the problem on your side (internet, hardware) or on MF's side (check ksef.podatki.gov.pl or the BIP announcement)?
2. Select the correct mode — offline24 (your problem), offline (MF announcement), or emergency (BIP MF declaration).
3. Issue the invoice in FA(3) format — sign the document with your Type 2 certificate.
4. Generate a printout/PDF with QR — hand the buyer a document containing the QR code and invoice number.
5. Store the invoice locally — keep the XML file until upload.
6. Upload to KSeF within the deadline — 1 business day (offline24/offline) or 7 business days (emergency).
7. Verify the UPO confirmation — after upload, confirm you received the Urzędowe Poświadczenie Odbioru (official acknowledgement of receipt) with the KSeF number.

FAQ

Is an invoice issued in offline mode valid for the buyer?

Yes. An invoice issued in any offline mode is a fully valid document from the moment the buyer receives it. The buyer may deduct input VAT (Art. 86(1) of the VAT Act) based on the offline invoice — they do not need to wait for it to appear in KSeF. The issue date on the invoice (not the upload date to KSeF) determines when the tax obligation arises.

What happens if I miss the upload deadline?

Missing the deadline does not invalidate the invoice — the buyer can still include it in their VAT settlement. However, the issuer faces an administrative penalty under Art. 106ni of the VAT Act. During the transitional period (through 31 December 2026), penalties are applied proportionally and take the taxpayer's good faith into account. After 2026, the penalty can reach up to 100% of the VAT amount on the invoice.

Can I use offline24 mode every day if my internet is unreliable?

Offline24 mode is designed for incidental situations, not as a permanent invoicing method. If you regularly lack a stable connection, invest in a backup link (e.g., an LTE router for 50–100 PLN/month) or switch your internet provider. Systematic use of offline24 may be challenged during an audit as circumventing the obligation to e-invoice in real time.

How do I check whether MF has declared a KSeF outage?

There are two sources: (1) a notice on ksef.podatki.gov.pl — this covers standard unavailability (offline mode); (2) a declaration in the Biuletyn Informacji Publicznej of the Ministry of Finance — this covers total outages (emergency mode). Most accounting software (Comarch, InFakt, Fakturownia) monitors the status automatically and displays an alert in its interface.

What about credit notes issued in offline mode?

Credit notes (correcting invoices) issued offline follow the exact same rules as original invoices. The FA(3) XML schema supports the "correction" document type — you upload it to KSeF within the same deadline as the source invoice. The buyer accounts for the correction from the date they received it, not from when it appears in KSeF.

Summary

A KSeF outage doesn't have to paralyze your business. The three fallback modes — offline24 (your problem, 1 business day), offline (MF announcement, 1 business day after downtime ends), and emergency mode (BIP MF, 7 business days) — give you real tools to keep operating. The key is preparation: download the Type 2 certificate now, make sure your software supports FA(3) and automatic upload, and train your team on the offline procedure. Because outages don't ask whether you're ready — they just happen.