If you run a company in Poland but do not do the bookkeeping yourself, KSeF (Poland's national e-invoicing system, Krajowy System e-Faktur) tends to fail in one specific way: nobody drew the line between what your accounting firm owns and what you own.
That line matters now. Mandatory structured invoicing reached the largest taxpayers on 1 February 2026 and the rest of active VAT payers on 1 April 2026. Throughout 2026, however, administrative fines are not applied. That transition ends on 31 December 2026.
Below is the minimum you should personally verify, even if someone else keeps your books.
What the 2027 penalties actually cover
Administrative fines for KSeF violations sit in Article 106ni of the Polish VAT Act and take effect on 1 January 2027. The catalogue of violations includes:
failing to issue a structured invoice through KSeF when required to do so,
issuing an invoice that does not follow the published schema during a declared outage or system unavailability,
failing to send an invoice issued outside KSeF into the system within the required deadline.
The amounts: up to 100% of the VAT shown on the invoice, or up to 18.7% of the total amount due when the invoice contains no VAT (exempt sales or a 0% rate, for example). Fines are imposed by decision of the head of the tax office and apply per invoice, so a repeated process error compounds.
One honest caveat that gets skipped in most summaries. The absence of administrative fines in 2026 does not mean nothing can happen. Fiscal penal liability for unreliable or defective documentation of transactions runs independently of Article 106ni.
Duty 1: sales invoices go through KSeF
If you are an active VAT payer, the obligation reached you on 1 April 2026. One exemption remains, and it expires shortly.
Businesses whose total monthly gross sales documented by invoices does not exceed PLN 10,000 may issue paper or electronic invoices outside KSeF until 31 December 2026. From 1 January 2027 the obligation covers everyone. The Ministry of Finance explains how the threshold is calculated on its KSeF portal.
Two traps in that threshold:
It only moves one way. You lose the right to invoice outside KSeF starting with the invoice that crosses PLN 10,000 in a given month. There is no route back, even if sales drop the following month.
Only invoiced sales count. A retail business selling PLN 22,000 in a month, of which PLN 19,000 goes through the cash register for consumers and PLN 3,000 covers three B2B invoices, counts only the PLN 3,000 toward the threshold.
Duty 2: purchase invoices arrive through KSeF
This one gets skipped because no fine attaches to it. Receiving structured invoices applies to every taxpayer holding a Polish NIP (tax identification number) since 1 February 2026, regardless of whether you are yet obliged to issue through the system.
The practical consequence: a supplier invoice will not land in your inbox. It sits in KSeF until somebody pulls it. If nobody does, the cost is not booked and the input VAT is not deducted on time. No Article 106ni fine, but a real cash cost.
Decide explicitly who retrieves purchase documents from KSeF and how often. That is a question for your accounting firm, not for yourself.
Duty 3: permissions, or who acts on your behalf
Permissions in KSeF are granted by the taxpayer, not by the accounting firm. How you do it depends on legal form:
Sole proprietorship (JDG, jednoosobowa działalność gospodarcza). You authenticate against your own NIP using Profil Zaufany (the state-run trusted profile), an e-ID card, or a qualified electronic signature. No filing is required.
Companies and other legal entities. If the entity holds a qualified electronic seal, it authenticates with that. If not, you designate the first authorised person using form ZAW-FA, filed with the head of the competent tax office. Foreign-owned Polish subsidiaries without a qualified seal usually land in this second path, so plan for the lead time.
An accounting firm can be authorised as an entity (by its NIP) or by naming individuals. The entity route is normally more practical, because staff turnover at the firm does not force changes on your side. Watch for the permission variant that allows onward delegation, since without it the firm cannot distribute access internally.
Permissions can also be scoped: issuing only, receiving only, or administration. Granting a firm full scope with no review process is the most common organisational mistake, and responsibility for the invoice stays with the taxpayer regardless.
Duty 4: what you do when there is no connection
Losing internet access does not suspend your invoicing obligation. Three special modes exist, and they differ only in how long you have to deliver the document into KSeF:
Mode When it applies Deadline to send to KSeF offline24 your own decision, when the problem is on your side by the next business day at the latest unavailability the Ministry of Finance announces downtime the next business day after it ends emergency mode the Ministry declares an outage in its official bulletin 7 business days from the end of the outage
In all three cases the invoice must follow the FA(3) schema, and the visualisation handed to the buyer outside the system carries two QR codes: an OFFLINE code granting access to the invoice in KSeF once it has been sent, and a CERTYFIKAT (certificate) code confirming the issuer's identity, which requires a KSeF certificate in the offline variant. The Ministry documents this in its offline24 section.
Worth asking yourself: who notices when an invoice issued late on Friday never reached KSeF? Late delivery of an offline invoice is named directly in the Article 106ni catalogue.
Duty 5: the KSeF number in payment transfers
From 1 January 2027, Article 108g of the VAT Act requires a buyer who is an active VAT payer to quote the KSeF number in the transfer title when paying a structured invoice issued by another active VAT payer.
Things worth knowing in advance:
Paying several invoices in one transfer means using a collective identifier generated in KSeF.
The duty applies only to payment instruments where a transfer title can be entered. Card payments, BLIK, and cash fall outside it.
The KSeF number is 35 characters long, so check now whether your banking interface accepts it in the title field.
Through the end of 2026, quoting the number in an ordinary transfer is voluntary. That makes this a good period to build the habit without risk.
Checklist: five things to close before 1 January 2027
Confirm whether you are relying on the PLN 10,000 monthly deferral, and whether a single larger invoice already ended it.
Log into KSeF with your own identity (Profil Zaufany, e-ID, or qualified signature) and review what permissions your accounting firm actually holds.
Agree in writing who issues sales invoices, who retrieves purchase invoices, and on what cadence.
Run one invoice through offline24 calmly, before you have to do it under pressure. Verify that your tool produces the required QR codes and that you hold a KSeF certificate in the offline variant.
Open your banking interface and check that the transfer title field accepts a 35-character KSeF number.
Wrapping up
You do not need to understand the FA(3) schema or quote Article 106ni. You need to know who in your company owns each of those five items, and to verify it before penalties become real on 1 January 2027.
Biurko is built for exactly this situation: KSeF authentication by certificate rather than token juggling, a multi-company panel with operation-level permissions, and KSeF error messages translated into language a non-accountant can act on, across Polish, English, and Ukrainian interfaces. Create a free account at biurko.io and see how your sales look in KSeF before the tax office does.
This article is not tax advice. For interpretive questions, consult an accountant or tax adviser.
FAQ
Will I be fined for KSeF mistakes in 2026? Administrative fines under Article 106ni of the VAT Act take effect on 1 January 2027, so there is no legal basis for imposing them during 2026. Fiscal penal liability for unreliable or defective documentation of transactions applies independently and is not suspended.
How large is the penalty for invoicing outside KSeF? Up to 100% of the VAT shown on that invoice. Where the invoice carries no VAT, the fine reaches up to 18.7% of the total amount due. These are maximums, imposed by decision of the head of the tax office, and they apply separately to each invoice.
Does a VAT-exempt sole proprietor have to use KSeF? Yes. From 1 April 2026 the obligation covers VAT-exempt taxpayers as well. The one exception is the deferral for businesses invoicing up to PLN 10,000 gross per month, which ends on 31 December 2026.
Can my accounting firm handle all of this for me? The firm can issue and receive invoices once you grant it permissions in KSeF, but only the taxpayer can grant those permissions, and responsibility for invoice correctness stays with the taxpayer. Define the permission scope and the review process in your service agreement.
What do I do if KSeF is unavailable when I need to issue an invoice? Issue the invoice in the FA(3) schema using offline24 and send it to KSeF by the next business day at the latest. If the Ministry of Finance declares an outage, you have 7 business days from the end of it. The visualisation handed to the buyer requires two QR codes.