KSeF Corrective Invoice (Faktura Korygująca): Complete 2026 Guide

Issuing a corrective invoice (Faktura Korygująca) in Poland's KSeF system has different rules than under the old paper or PDF system. This guide covers exactly what you need to do in 2026.

What Changed with KSeF for Corrective Invoices

Before the KSeF mandate, a corrective invoice (credit note) referenced the original invoice's own number — the sequence number you assigned. Under KSeF, every invoice receives a KSeF reference number (numer KSeF) from the government system. Your corrective invoice must now reference this KSeF number, not just your internal number.

This is the single biggest source of errors for businesses new to KSeF corrections.

Types of Corrections in KSeF

KSeF supports two types of corrective documents:

Faktura Korygująca (Full correction): Replaces incorrect fields with correct values
Nota Korygująca (Buyer's correction note): For minor errors in buyer data — issued by the buyer, not the seller

For most corrections (price, quantity, VAT rate, date), use Faktura Korygująca.

Step-by-Step: Issuing a Corrective Invoice for a KSeF Invoice

Step 1: Locate the Original KSeF Number

Every invoice issued through KSeF has a unique reference number in the format YYYYMMDD[hash]. Find this in:

Your accounting software's KSeF dashboard
The KSeF portal (ksef.mf.gov.pl) under your tax account
The XML of the original invoice: <NumerKSeF> field

Step 2: Include the KSeF Reference in Your Correction

In your FA_VAT XML, the corrective invoice must include:

<Fa>
  <KodWaluty>PLN</KodWaluty>
  <P_1>2026-05-13</P_1>
  <!-- Correction type flag -->
  <RodzajFaktury>KOR</RodzajFaktury>
  <!-- Reference to original KSeF number -->
  <DaneKorygowane>
    <NumerKSeF>[original KSeF number here]</NumerKSeF>
    <NrFaKorygowanej>[your original invoice number]</NrFaKorygowanej>
    <DataWystFaKorygowanej>2026-04-01</DataWystFaKorygowanej>
  </DaneKorygowane>
  <!-- ... corrected line items ... -->
</Fa>

Step 3: Submit Through KSeF Like Any Invoice

Submit your corrective invoice XML through your software's KSeF API connection. It will be validated and receive its own new KSeF reference number.

Step 4: Notify Your Customer

Once KSeF issues the new reference number for your corrective invoice, your customer will see it in their KSeF account. Your software should also send them the correction notification.

Correcting Pre-KSeF Invoices (Before February 2026)

If you need to correct an invoice that was issued before the KSeF mandate (before 1 February 2026 for large businesses, before 1 April 2026 for others), the rules are different:

The correction must still go through KSeF, but uses a special reference field for pre-KSeF invoices:

<DaneKorygowane>
  <!-- No NumerKSeF field — use this instead: -->
  <NrFaKorygowanej>INV-2025-001</NrFaKorygowanej>
  <DataWystFaKorygowanej>2025-12-15</DataWystFaKorygowanej>
</DaneKorygowane>

Your accounting software should handle this automatically if you mark the invoice as "pre-KSeF" when creating the correction.

Common Errors When Issuing Corrections

Error Code	Meaning	Fix
`FA_VAT_ERR_301`	Referenced KSeF number not found	Double-check the NumerKSeF value
`FA_VAT_ERR_302`	Original invoice does not belong to your NIP	Verify you are referencing your own invoice
`FA_VAT_ERR_303`	Correction period too long	KSeF does not enforce a time limit, but ANAF does — check VAT settlement period
`FA_VAT_ERR_401`	RodzajFaktury missing or wrong	Must be `KOR` for corrections

Nota Korygująca: Buyer-Side Correction

If your customer needs to correct their own data (buyer name, address, buyer NIP), they issue a Nota Korygująca. This goes through KSeF from the buyer's account, not yours. You must confirm acceptance of the Nota in the KSeF system.

Key Takeaways

Always use the KSeF reference number (not just your invoice number) in corrections
Pre-KSeF invoices use a different reference structure — no NumerKSeF field
RodzajFaktury must be set to KOR for corrective invoices
The Ministry of Finance updated the FAQ in May 2026 to clarify that corrective invoices for pre-KSeF period use the pre-KSeF reference fields

KSeF Corrective Invoice Guide: How to Issue Faktura Korygująca in 2026