Fake invoice in KSeF: what to do

You can't reject a fake invoice in KSeF (Krajowy System e-Faktur, Poland's National e-Invoicing System), because the system has no such option. Don't pay it or deduct VAT from it, check the seller on the Biała Lista (the VAT taxpayer register), and if you suspect fraud, report the invoice in the Aplikacja Podatnika with the "Zgłoszenie nadużycia" ("report abuse") button.

Why a stranger's invoice lands in your account

KSeF assigns an invoice to the recipient based on the NIP (tax identification number) the issuer enters in the buyer field, and there is no "accept" step on your side. You see the invoice on the recipient's side like any other (how to receive an invoice in KSeF). Your NIP is public (CEIDG for sole traders, KRS for companies), so a dishonest business can simply type it in.

KSeF 2.0 Manual, Part II, sections 5 and 6.3

Wrong NIP or fraud

Mistake. The issuer transposed digits and entered your NIP instead of the right recipient's. Contact the seller and ask for a zeroing correction and a new invoice with the correct NIP.

Fraud. Warning signs (our practical pointers, not an official MF checklist):

• you don't know the company and have never dealt with it,
• the service description means nothing to you, and the text reads like machine translation,
• the phone rings out and email bounces,
• the payment deadline is absurdly short (three or five days),
• the seller isn't on the Biała Lista (Wykaz Podatników VAT); that is a reason to check further, since not every seller is listed (see step 2).

What to do, step by step

1. Don't pay and don't book it

KSeF has no option to approve or reject invoices; disputes are settled outside the system. If the transaction never happened, don't pay the invoice, don't book it and don't deduct VAT from it. That is our advice: whether the invoice goes into your records is a decision for you and your accountant, not something its appearance in KSeF settles.

KSeF 2.0 Manual, Part II, section 6.3

You receive an invoice from KSeF on the day it is assigned its KSeF number (Art. 106na(3) of the VAT Act). The right to deduct VAT arises in the period in which the tax obligation arose, but no earlier than the period in which you received the invoice (Art. 86(10b)(1)). The deduction itself also requires meeting the conditions of Art. 86 and the absence of any exclusion under Art. 88.

Polish VAT Act, Art. 86(10b)(1), Art. 106na(3) KSeF 2.0 Manual, Part II, sections 1.7 and 5.1 MF, KSeF FAQ, question 1

2. Check the seller on the Biała Lista

Enter the NIP from the invoice in the Wykaz Podatników VAT. In our view, an entry with details matching the invoice points towards a mistake, although it doesn't rule out a fraudster using a real company's details. In that case write to the seller, ideally using contact details from CEIDG, KRS or the company's website rather than from the invoice, and ask for a correction. Details that don't match the invoice are a strong sign of fraud: don't wait for the seller to reply and go to step 3. A missing entry proves nothing by itself, because the register lists only taxpayers registered for VAT (plus those refused registration or removed). A seller exempt under art. 113 who never registered isn't there, yet has also invoiced in KSeF since 1 April 2026. Check such a seller in CEIDG or KRS and contact them.

Polish VAT Taxpayer Register (Biała Lista)

3. Report the abuse in the Aplikacja Podatnika

Log in to the Aplikacja Podatnika KSeF (the taxpayer web app) at ap.ksef.mf.gov.pl and use the "Zgłoszenie nadużycia" ("report abuse") button. Reports go to KAS (Krajowa Administracja Skarbowa, the National Revenue Administration). Because of tax secrecy, KAS doesn't tell the reporter how the check went or what the result was. Don't report an invoice issued by mistake as fake; a correction from the seller is enough there.

KSeF 2.0 Manual, Part III, section 7 (incl. 7.4)

MF has also announced a way to hide invoices, but according to the Manual of 6 August 2026 that feature isn't available yet. A hidden invoice won't disappear from KSeF, and the seller won't be told. According to MF, reporting and hiding an invoice create no new obligations for the taxpayer.

KSeF 2.0 Manual, Part III, sections 7.2 and 8.2 KSeF 2.0 Manual, Part II, section 6.3

4. Tell your accountant

Your accounting firm sees your invoices but doesn't know your contracts. With automatic KSeF import, a suspicious invoice can be booked in routine work, especially at month-end. Tell them plainly: "This invoice is suspicious, please don't book it until this is resolved". If it has already reached the records, ask them to take it out before the period closes, and ask whether their software can flag invoices from unknown counterparties before import.

Reducing the risk

Nothing fully protects you from a fraudster entering your NIP. KSeF doesn't send notifications about new invoices, so two habits help: check KSeF every few days instead of once a month, and agree with your accountant that an invoice from a new company needs your confirmation first.

KSeF 2.0 Manual, Part II, section 6.4

Phishing that impersonates KSeF

Also watch out for emails that may impersonate the Ministry of Finance or KSeF, with "login" links and requests for your details (general caution, not a report of any particular wave of scams). Our advice: don't click links in messages about KSeF. Go to ksef.podatki.gov.pl and the Aplikacja Podatnika by typing the address or from a bookmark.

If the stranger's invoice turned out to be a plain NIP mistake, the next step is the zeroing correction.