Wrong Buyer NIP on a KSeF Invoice: The Only Correct Procedure

You issued an invoice through KSeF with the wrong buyer NIP. The system accepted it, assigned a KSeF number, and issued a UPO. The invoice is now in legal circulation, visible to whatever real entity holds that NIP. You cannot edit it. You cannot cancel it. You cannot issue a nota korygująca, because the buyer-issued correction note was abolished on 1 February 2026.

The fix requires three documents and a conversation with your buyer. There is no shortcut.

Why KSeF Did Not Catch the Error

The Ministry of Finance confirmed in its FAQ that KSeF validates only FA(3) schema compliance and sender permissions. It does not check buyer data against the tax registry. A schema-compliant invoice with a mistyped NIP passes validation, receives a KSeF number, and enters legal circulation. The system does not know whether the NIP belongs to your actual customer, to a completely unrelated company, or to no one at all.

This means the wrong-NIP invoice has already been delivered to whatever entity holds that NIP. If the NIP belongs to a real, active taxpayer, that company can see your invoice in their KSeF inbox. You cannot undo this. The invoice remains visible to them permanently. There is no recall, no delete, no retroactive removal.

The Three-Document Procedure

Document 1: Korekta do zera (Zeroing Correction)

Issue a faktura korygująca that reduces every line of the original invoice to zero. This correction must reference the original invoice's KSeF number and use the wrong NIP, not the correct one. The correction zeroes out the original invoice in the eyes of the tax authority, but it does not remove the original from the wrong buyer's KSeF inbox.

The legal basis is art. 106j ust. 2 pkt 2 lit. a of the VAT Act. The correction must be issued by the seller (you), not the buyer. The buyer-issued nota korygująca was repealed on 1 February 2026 when art. 106k was abolished.

Key fields:

• Reference the original invoice number and KSeF number
• Use the wrong NIP (the same one as the original)
• Set all line items to zero
• Set the correction reason (przyczyna korekty is optional under art. 106j ust. 2a, despite content farms claiming it is mandatory)

Document 2: New Original Invoice

Issue a brand-new invoice with the correct buyer NIP. This invoice gets a new invoice number, a new issue date, and a new KSeF number. It is not a correction. It is a fresh original invoice.

Key considerations:

• New invoice number from your numbering sequence
• Issue date is today (the date you are issuing the new invoice, not the date of the original)
• Correct buyer NIP, verified against the biała lista before submission
• All line items, amounts, and VAT rates from the original invoice
• Submit through KSeF as a normal invoice

Document 3: Buyer Notification

Contact your buyer directly. Tell them what happened. They need to know:

• The original invoice with the wrong NIP is visible in someone else's KSeF inbox
• A zeroing correction has been issued against the original
• A new invoice with the correct NIP is on its way
• They should book the new invoice, not the original

This conversation is not optional. If the buyer's accountant books the original invoice (which they might, if they see it in their system before you call), they will claim input VAT on an invoice that has been zeroed out. The mismatch creates reconciliation work for both parties.

What Not to Do

Do not try to cancel the invoice. KSeF has no cancel, annul, or delete function. Once a KSeF number is assigned, the invoice exists permanently.

Do not issue a nota korygująca. The buyer-issued correction note was abolished on 1 February 2026. Even if your buyer offers to issue one, it has no legal effect in KSeF.

Do not try to fix the NIP outside KSeF. Editing your local copy of the invoice, sending a corrected PDF, or issuing a new invoice without zeroing the original creates a parallel set of records that does not match what KSeF holds. The tax authority sees the original invoice with the wrong NIP as still active.

Do not ignore the problem. The original invoice with the wrong NIP is visible to a stranger. If that entity books it as a purchase, both their and your tax records are contaminated. The zeroing correction is what tells the tax authority the original should not be counted.

Scenario: One Digit Off

A consulting sp. z o.o. issues an invoice for 12,000 PLN + 23% VAT through KSeF. Three days later, the buyer's accountant says they cannot see the invoice in their KSeF inbox. The seller checks and discovers the buyer NIP differs by one digit: 7010001234 instead of 7010001235.

The wrong NIP belongs to a real, active taxpayer. That company can now see the consulting invoice in their KSeF inbox. The seller cannot remove it.

The seller issues a korekta do zera referencing the original invoice's KSeF number, using the wrong NIP (7010001234). All line items are set to zero. The correction is submitted to KSeF and receives its own KSeF number.

The seller then issues a new original invoice with the correct NIP (7010001235), a new invoice number, today's date, and the same 12,000 PLN + 23% VAT. This invoice is submitted to KSeF and receives its own KSeF number.

The seller calls the buyer, explains the situation, and confirms which invoice number and KSeF number to book.

Total documents in KSeF: three. The original (wrong NIP, still visible to the stranger), the zeroing correction, and the new original. The tax authority sees the original and the correction netting to zero, plus the new original as the active invoice.

Prevention: Verify Before Sending

The wrong-NIP procedure is painful enough that prevention is worth the effort. Before submitting any invoice to KSeF:

1. Check the NIP checksum. The 10-digit NIP has a control digit calculated from the first 9. If the checksum fails, the NIP is wrong.
2. Look up the NIP on the biała lista podatników VAT. This confirms the NIP belongs to an active VAT taxpayer and matches your buyer's legal name.
3. Check VIES for EU buyers. If you are invoicing a EU client, verify their VAT ID in the VIES database before issuing.
4. Use a contractor card, not free-text entry. Store verified NIPs in your contractor database and pull from there, rather than typing the NIP manually on each invoice.

Plandesk performs all four checks automatically before submission. The NIP is validated against the checksum, looked up on the biała lista, and compared to the contractor record. If the NIP does not match, the invoice is blocked before it reaches KSeF. The wrong-NIP procedure exists for when prevention fails. It should not be your primary strategy.

This material is information of a general nature and does not constitute legal or tax advice. For a specific situation, verify the current rules or consult a qualified adviser.