How to fix a wrong buyer VAT ID on a KSeF invoice?

One wrong digit in a buyer NIP and your invoice sits in the KSeF account of a company you have never traded with. Until January 2026 this was a two-minute problem. The buyer issued a corrective note (nota korygująca), the seller accepted it, done.

That route no longer exists. If your group runs a Polish subsidiary or you invoice Polish counterparties, this changes who owns the fix and when it hits your VAT return. Below is the procedure, the technical reason behind it, and the cases it does not cover.

What disappeared on 1 February 2026

The act of 5 August 2025 introducing mandatory KSeF (Poland's national e-invoicing system), published as Dz.U. 2025 poz. 1203, repealed Article 106k of the VAT Act. That provision let the buyer correct formal details on a received invoice: its own name, address and NIP.

The repeal is absolute. Corrective notes cannot be issued inside KSeF, outside KSeF, against structured invoices or against paper ones. Asking the seller to accept such a document changes nothing, because acceptance of an instrument the statute no longer recognises does not create a correction invoice.

Only historical documents keep their status. A note issued before 1 February 2026 is judged under the rules in force on its issue date, so a January note accepted in March remains valid.

From that date the burden sits entirely with the seller. The legal hook is Article 106j(1)(5) of the VAT Act: a correction invoice is required whenever an error is found in any item of an issued invoice.

Why zeroing, rather than a simple data fix

This part is worth understanding, because the procedure looks heavier than the error.

Once KSeF accepts a structured invoice it assigns a KSeF number, and the document becomes available to whoever holds the NIP written on it. If that NIP belongs to a real business, the invoice is already sitting in their account. You cannot pull it back, because a structured invoice cannot be cancelled.

The FA(3) logical structure also has no mechanism for a correction that rewrites the buyer's tax identification fields. A correction points at one specific document issued to one specific party. Changing the NIP would mean correcting an invoice that was issued to somebody else.

So the Ministry of Finance, in the KSeF 2.0 Manual published at ksef.podatki.gov.pl, sets out a single valid path: the seller zeroes the faulty invoice with a correction, then issues a new original invoice to the correct buyer. This is the Ministry's position in its KSeF guidance rather than a provision of the statute itself, so for an unusual case it is worth confirming it with your accountant.

One detail catches people out. The zero correction must carry the same wrong NIP as the original invoice. It corrects a document issued to that entity. The correct NIP appears only on the new invoice.

Step by step

Step 1. Scope the error. Check whether the NIP exists and who holds it. If it belongs to a real company, tell them a document arrived that is not theirs and warn them a correction is coming.

Step 2. Issue the zero correction. Every line drops to zero: quantity, unit price, net, VAT, gross. State a specific reason, for example "incorrect buyer NIP on the original invoice". Send it to KSeF.

Step 3. Issue the new original invoice. Same lines, same amounts, same supply date, correct buyer. This is not a new transaction, it is correct documentation of the same supply.

Step 4. Settle the accounting period. A zero correction is a downward correction, so the seller follows Article 29a(13)–(14) of the VAT Act: a structured correction issued online is recognised in the period in which it is sent to KSeF. The new original invoice is recognised under the ordinary rules for an original invoice. The two periods may therefore differ, so confirm the treatment with your accountant.

The economic effect is neutral: the original invoice is reversed by the correction, leaving a single real taxable supply to the correct buyer. Because the periods in which the correction and the new invoice are recognised may differ, check with your accountant that output VAT is not reported twice in any period.

What this rule does not cover

Zeroing is the remedy for a NIP error, not for every mistake.

A typo in the buyer's name or a stale address with a correct NIP does not need zeroing. The document reached the right entity, so an ordinary correction of formal details is enough. Zeroing here means three documents where one would do.

Invoices issued outside KSeF follow the same rule on corrective notes: they are gone. But the technical constraint that forces zeroing applies to a document that already exists in the system under a stranger's account. Outside the system, correcting identification data remains workable.

Invoices issued in offline24 mode reach KSeF with a delay. Catch the error before transmission and you simply fix your own document. Once a KSeF number is assigned, the full procedure applies.

B2C sales without a buyer NIP never hit this problem.

How this works in Biurko

In Biurko the zero correction is a single action on the invoice. You choose the "Correct to zero" action, the system creates a draft KOR document (with the correction type set to "error" and the default reason "Correction to zero", which you can make more specific before issuing), copies every line with zeroed amounts and carries over the buyer details from the original, including the wrong NIP. Nothing to retype, and no risk of quietly "fixing" the NIP inside the correction itself.

The replacement invoice does not need retyping either. Duplication copies lines and settings from the original, and you change only the counterparty. A NIP lookup against the Polish business register (GUS) pulls official registration data, which makes a repeat of the same error less likely.

Only one draft correction can exist per invoice at a time. Click the action twice and you land back in the existing draft rather than generating a second document. In an accounting office with several people touching the same client, that guardrail saves a lot of explaining.

Checklist for a wrong NIP

1. Check whether the wrong NIP belongs to a real entity and notify them.

2. Issue the zero correction carrying the same wrong NIP.

3. Write a specific reason, not a generic "error".

4. Send the correction to KSeF and wait for the KSeF number and the UPO (official receipt confirmation).

5. Issue the new original invoice with the correct NIP and the same supply date.

6. Agree with your accountant the period for the correction and for the new invoice (Article 29a(13)–(14) of the VAT Act).

7. Keep a note linking the three documents for audit purposes.

Summary

Removing corrective notes moved full responsibility for data accuracy onto the issuer. A wrong buyer NIP stopped being a formality and became a three-document procedure. The upside is that the procedure is predictable, which means it can be automated.

In one action Biurko creates a draft zero correction with the buyer details from the original invoice, and you prepare the new invoice from a duplicate. You issue and send each document to KSeF separately (automatic sending on issue is off by default), and a trail stays in each document's history. Create a free account at biurko.io. To practise without legal effect, use the Biurko demo (demo.biurko.io, 7-day access, the KSeF demo environment). An account on app.biurko.io sends invoices to production KSeF, so every invoice you send there is real.

FAQ

Can I still issue a corrective note for a 2025 invoice? No. What matters is the date of the corrective act, not the date of the original invoice. Since 1 February 2026 the enabling provision no longer exists, so every fix requires a correction invoice from the seller.

Who issues the zero correction, the seller or the buyer? The seller only. After the repeal of Article 106k the buyer has no instrument for self-correction. Their role is to report the error and wait for the documents.

Does the zero correction plus a new invoice mean paying VAT twice? It should not. The zero correction reverses the output VAT on the original invoice and the new invoice reports it against the correct buyer, leaving one taxable supply in the return. Because the periods in which the two documents are recognised may differ, confirm the treatment with your accountant.

Which NIP goes on the zero correction? The wrong one, identical to the original invoice. The correction refers to a specific document issued to that entity. The correct NIP appears only on the new original invoice.

Does a wrong company name with a correct NIP also require zeroing? No. If the NIP is right, the invoice reached the right entity and a correction of formal details is sufficient. Zeroing applies where the document physically landed in a stranger's KSeF account.