Deleting a KSeF invoice: what to do instead

Once KSeF (Krajowy System e-Faktur, Poland's National e-Invoicing System) has assigned an invoice a number, you can't delete, cancel or edit it: the invoice has entered legal circulation, and KSeF stores it for 10 years from the end of the year it was issued. The issuer fixes a mistake with a corrective invoice (faktura korygująca), and if KSeF rejected the file without assigning a number, the invoice was never issued at all, so you fix the data and send it again. KSeF 2.0 Handbook, part II, sections 1.6.1–1.6.3 and 7

Legal position as of 20 October 2026.

A KSeF number means the invoice already exists

The VAT Act defines a structured invoice as an invoice issued using KSeF together with its assigned number. It counts as issued on the day it is sent to KSeF, and as received on the day the number is assigned. VAT Act, consolidated text (Dz.U. 2026 poz. 1263), Art. 2(32a) and Art. 106na(1) and (3)

From that moment there's no undoing it. According to Poland's Ministry of Finance (MF), taxpayers can't delete invoices themselves, even when the buyer is wrong. KSeF 2.0 Handbook, part II, section 1.6.3 The KSeF API, which invoicing software uses, has no such operation either. KSeF API, open-api.json and api-changelog.md (up to version 2.9.0) An invoice sent on 5 February 2026 stays in the system until 31 December 2036. KSeF 2.0 Handbook, part II, section 7 MF, frequently asked questions, question 21

KSeF rejected the file: fix it and send it again

When an invoice sent online fails verification, KSeF assigns no number, and according to MF that means the invoice has not been issued. There's nothing to delete or correct. Files are rejected for reasons such as not matching the FA(3) schema, missing permissions, or an issue date in the future. KSeF 2.0 Handbook, part II, section 1.6.1

Got an XML file that KSeF didn't accept? Drop it into the validator: it shows errors in the file's structure and content (it doesn't check permissions or duplicates). Your file never leaves your browser. You then resend the corrected invoice without worrying about order: KSeF doesn't check that numbering is sequential, so an invoice with an earlier number can reach the system after invoices with later numbers. KSeF 2.0 Handbook, part II, section 1.6.7

An offline invoice rejected for technical reasons (for example a schema mismatch, a duplicate, or a file that's too large) can be resent by your software as a so-called technical correction (korekta techniczna). This doesn't apply to a rejection for missing permissions. The content of the invoice must not change. KSeF API, technical correction Aplikacja Podatnika (MF's free invoicing app) issues online invoices only, so you won't run into this there. MF, frequently asked questions, question 11 More on offline mode is in our guide to KSeF outages.

A mistake in an accepted invoice is fixed by a correction

If a mistake is found in any item of an invoice after it was issued, the taxpayer issues a corrective invoice. VAT Act, consolidated text (Dz.U. 2026 poz. 1263), Art. 106j(1) That's how you fix the buyer's name and address, amounts, tax rate, date and even the invoice number. FA(3) logical structure: Podmiot2K, NrFaKorygowany KSeF doesn't check the arithmetic, so an invoice with miscalculated VAT still gets a number and needs a correction too. KSeF 2.0 Handbook, part II, sections 1.6.1 and 1.6.2

Only the issuer of the original invoice (usually the seller) can issue the correction. Corrective notes (noty korygujące) no longer exist from 1 February 2026, including for invoices issued outside KSeF, so the buyer reports the mistake to the seller outside the system. VAT Act, consolidated text (Dz.U. 2026 poz. 1263), Art. 106k (repealed) KSeF 2.0 Handbook, part II, sections 1.6.2 and 6.3 The details are in our post on the corrective note.

Wrong buyer NIP: correct to zero and issue a new invoice

Olena runs a JDG (jednoosobowa działalność gospodarcza, a Polish sole proprietorship) doing translations. On an invoice for an accounting firm she entered another client's NIP (Polish tax identification number). The invoice went to the company that holds that NIP. A wrong NIP isn't fixed by correcting it to a different one. Olena corrects the invoice to zero, leaving the wrong NIP in it, and issues a new invoice with the right one. KSeF 2.0 Handbook, part II, sections 1.6.3 and 1.6.4

A zero-value correction doesn't cancel the invoice. The original invoice and the correction both stay in KSeF. How to fill in such a correction is shown in zero-value correction when the buyer's NIP is wrong.

A test invoice sent to production

Marek, a developer, was testing his company's system integration with KSeF and sent a dummy invoice to the production environment by mistake. Since it got a KSeF number, it's a fully valid invoice that documents no transaction, which may mean having to pay the tax under Article 108 of the VAT Act. It has to be corrected to zero without delay. KSeF 2.0 Handbook, part II, section 3.2.3

The test and demo environments work the other way round: documents sent there aren't invoices and have no legal effect. KSeF 2.0 Handbook, part II, sections 3.2.1 and 3.2.2

The same invoice sent twice

Tomasz runs a bike shop. After a dropped connection, his software sent the same invoice a second time, even though the first submission had reached KSeF and received a number. KSeF recognises a duplicate by the seller's NIP, the invoice number and the invoice type, and rejects the second copy with error code 440 „Duplikat faktury” ("Duplicate invoice"). The second copy has no number, so there's nothing to delete. KSeF enforces invoice uniqueness for 10 full years from the end of the year of issue. KSeF API, invoice verification: duplicates

It's different if you invoice the same sale twice under two different numbers. Both invoices pass verification, and in the MF materials we analysed we found no description of how to fix such a mistake.

You received an invoice you don't want

The buyer can't delete anything either. KSeF has no option to accept or reject invoices, and the seller and buyer resolve disputes over whether an invoice is justified, or over mistakes in it, outside the system. KSeF 2.0 Handbook, part II, sections 6.1 and 6.3

MF announced an option to hide an invoice, to be rolled out a few months after KSeF 2.0 launched. KSeF 2.0 Handbook, part II, section 6.3 Part III of the handbook, dated 6 August 2026, describes the feature as not yet available, and a hidden invoice doesn't disappear from KSeF. KSeF 2.0 Handbook, part III, section 8 We haven't checked whether it works today. If the invoice looks like an attempted fraud, see our post on fake invoices in KSeF for what to do.

What MF hasn't settled

In the MF materials we analysed, we found no answer to two questions:

• whether an offline invoice that has been issued but not yet sent to KSeF can be withdrawn, or simply not sent,
• whether an invoice issued outside KSeF can be cancelled: a paper or PDF invoice within the 10,000 zł monthly limit (Art. 145m), a cash-register invoice (Art. 145n), or one for a private individual.

Invoices outside KSeF are corrected the same way, with a corrective invoice, because Art. 106j(1) applies to every invoice.

Have a KSeF number and a mistake on the invoice? Our post on corrective invoices in KSeF walks through the correction step by step.