Myth 1: "KSeF will be postponed again — it isn't live yet"
It won't be. The schedule is written into the amended VAT Act and rolls out in stages:
From Who must issue invoices in KSeF 1 February 2026 companies whose 2024 sales (incl. VAT) exceeded PLN 200 million 1 April 2026 all other active VAT taxpayers 1 January 2027 the smallest sellers — invoiced sales up to PLN 10,000 gross per month
The full timeline and legal basis are published on ksef.podatki.gov.pl.
If you run an ordinary VAT-registered business and aren't a billion-zloty corporation, your deadline was 1 April 2026 — for most readers, that's already in the past, not the future.
Myth 2: "KSeF only affects large companies, not my small business"
This is a half-truth that bites. The obligation to issue invoices arrived in stages, but the obligation to receive invoices through KSeF applied to every business from 1 February 2026, regardless of size. Your supplier can issue you an invoice in KSeF and will not email it. If you never open the system, you simply won't see it.
The second point is the famous PLN 10,000 threshold. It is not a "small-business exemption." It's a monthly cap on the total value of invoices issued outside KSeF — VAT included, from any source (shop, marketplace, B2B by email). Exceed it in a given month and that invoice must go through KSeF, with no grace period. And the threshold only lasts until the end of 2026 — from 1 January 2027 everyone is in.
The scope of the obligation is set out on the official MF page.
Note on terms: JDG (jednoosobowa działalność gospodarcza) is a Polish sole proprietorship; NIP is the Polish tax ID; MF is the Ministry of Finance.
Myth 3: "I have to issue consumer (B2C) invoices in KSeF too"
You don't. Invoices to private individuals who are not running a business may be issued in KSeF voluntarily — the choice rests with you as the seller (source: MF).
In practice this means a consumer invoice follows a different path than a B2B invoice. Good software should tell them apart automatically and mark the document as issued outside KSeF, so you don't accidentally push data into the system that never needed to be there.
Watch for one trap: if a private individual asks for an invoice and provides a NIP, the transaction changes character — it becomes a buyer-identified path, not plain B2C.
Myth 4: "If KSeF goes down or I lose internet, I can't issue an invoice"
You can. The legislator anticipated outages and defined what to do. In short:
Offline24 mode (the system is unavailable but MF has not declared an official outage) — you issue the invoice outside KSeF and send it to the system by the next business day at the latest.
Outage declared by MF in the official bulletin (BIP) — you have 7 business days to submit the invoices after it ends.
In both cases sales continuity is preserved — you issue the invoice "for now," and it reaches KSeF with the right flag (in the JPK file, the OFF marker). You can monitor the current system status via MF announcements.
The practical takeaway: offline mode isn't a rare exception to ignore — it's a standard part of the process. Your invoicing tool must support it, not block a document "because there's no connection."
Myth 5: "I'll be fined for every KSeF mistake straight away"
Not in 2026. The whole of 2026 is a transition period: tax authorities are not imposing administrative penalties for technical slips, submission delays, or errors caused by rolling out the system.
The administrative penalties set out in the VAT Act take effect only from 1 January 2027, and they are steep:
up to 100% of the VAT shown on the invoice (when a document was issued outside the system despite the obligation),
up to 18.7% of the total amount for invoices with no VAT shown (e.g. VAT-exempt taxpayers).
A concrete figure: an invoice of PLN 100,000 net (VAT PLN 23,000) issued outside KSeF after 1 January 2027 carries a penalty of up to PLN 23,000 — for a single document.
Just don't confuse "no penalties" with "anything goes." Already today, a paper invoice from an entity that is subject to the obligation is not a valid invoice under the Act — your counterparty cannot deduct VAT from it. Fiscal-penal liability also applies. The absence of administrative penalties in 2026 is time to get your processes right, not to postpone them.
Checklist: act before the myths catch up with you
Check your deadline — if you're under PLN 200 million, your issuing obligation started on 1 April 2026.
Turn on KSeF invoice receiving now — mandatory for everyone since 1 February 2026.
Separate your B2B and B2C flows — don't push consumer invoices into KSeF unless you want to.
Test offline24 mode before you actually need it — confirm your system can issue an invoice with no connection.
Generate KSeF 2.0 authentication (a KSeF certificate or a qualified signature/seal) — don't leave it to the last minute.
Use 2026 as a buffer — fix your processes while mistakes don't end in fines.
Verify changes at the source — KSeF rules are still being refined; rely on MF announcements, not hearsay.
Conclusion
The costliest KSeF myth is the belief that "it isn't here yet." It is, it's mandatory, and 2026 is the last window to prepare without risking penalties. The rest — about large companies, B2C, outages and sanctions — collapses the moment you check it against the Act.
Biurko walks you through KSeF so you don't have to memorize every exception: it separates B2B from B2C, handles offline24 mode, and tracks deadlines for you. Try Biurko free for 14 days at biurko.io and stop guessing what applies to you.
FAQ
Is KSeF already mandatory in 2026? Yes. From 1 February 2026 for companies with sales above PLN 200 million, and from 1 April 2026 for all other VAT taxpayers. The smallest sellers (up to PLN 10,000 gross per month) join on 1 January 2027. Receiving invoices through KSeF has applied to everyone since 1 February 2026.
Do small businesses and sole proprietors have to use KSeF? Yes, in stages. Receiving invoices applies to everyone from 1 February 2026. Issuing starts on 1 April 2026, while the smallest sellers (under PLN 10,000 gross per month) have until 1 January 2027. That threshold is a transitional cap, not a permanent exemption.
Do I have to issue consumer invoices in KSeF? No. Invoices to private individuals not running a business (B2C) can be issued in KSeF voluntarily — it's the seller's choice. However, if the buyer provides a NIP (Polish tax ID), the transaction is treated differently from ordinary consumer sales.
What do I do when KSeF is unavailable? You issue the invoice in offline mode. If MF hasn't declared an outage, send the document to KSeF by the next business day. If an outage is announced in the BIP bulletin, you have 7 business days after it ends. Sales can continue without interruption.
When do penalties for not using KSeF start? Administrative penalties (up to 100% of the VAT on the invoice) take effect from 1 January 2027. 2026 is a transition period with no administrative penalties for errors. Fiscal-penal liability still applies, and a paper invoice from an obligated entity does not grant the right to deduct VAT.