Invoice Correction in Poland (2026) — Credit Note, Storno, Discounts
Invoice corrections in 2026 in Poland — correcting note (FK), storno, discounts, goods returns. When, how, and why. A practical guide with examples.
Issued an invoice with an error? Or a client returned goods? You need to issue a correction. But beware — a correction is not the same as a duplicate. And a mistake in the correction can double your VAT or zero it out.
In this guide, I explain the rules for invoice corrections in Poland in 2026.
Types of Corrections
Invoice correction (FK) — when to issue and how does it work?
A correcting invoice (FK) modifies the original invoice after it has been issued. It must contain a reference to the original invoice number and an explanation of the correction reason.
When to issue a correcting invoice?
Granting a discount after issuing the invoice (e.g. volume discount, loyalty)
Buyer returns goods after the invoice has been issued
Incorrect price, VAT rate, or quantity on the original invoice
Transaction cancellation, mistaken invoice, goods not received
Example: discount after issuing the invoice
VAT impact for the seller
When FK lowers the amount — the seller reduces output VAT
When FK raises the amount (e.g. upward correction) — the seller increases output VAT
A correcting invoice must contain: the word „CORRECTION", the original invoice number, the reason for correction, the amounts before and after correction, and the difference.
Key rule: A correcting invoice does not replace the original invoice — it modifies it. An FK must always reference the original invoice number. Without this reference, the document is not a correcting invoice.
Need to issue a correction or received an FK from a contractor?
I can help →Based on Art. 106j of the VAT Act. A correcting invoice is issued when the tax base changes before or after the payment deadline (additional conditions apply).
1. Correcting Invoice (FK / Credit Note)
You issue one when amounts change on the invoice — e.g., a discount, goods return, price error.
2. Correcting Note
Issued by the buyer (not the seller), when the error concerns the buyer's data (e.g., wrong VAT number, address).
When to Issue a Correction?
Post-Sale Discount
The client is owed a discount (e.g., for loyalty, defective goods). You issue a credit note for the discount amount.
Goods Return
The client returns the goods. You issue a credit note reducing revenue and VAT.
Price or Quantity Error
You invoiced 10 units instead of 8? Correction.
Storno (Invoice Cancellation)
The client didn't pay, the invoice was erroneous. You issue a "storno" credit note — it zeroes out the original invoice.
What Must a Correction Contain?
- The word "CORRECTION" or "CORRECTING INVOICE"
- The original invoice number (linkage)
- The correction issue date
- Before correction / After correction — net, VAT, gross amounts
- Reason for correction (discount, return, error)
- Signatures (not mandatory since 2020, but recommended)
Example Credit Note (10% discount):
CORRECTING INVOICE no. FK/2026/001
Pertains to invoice: FV/2026/0123 dated 15.01.2026
Reason: Loyalty discount 10%
Before correction: 5,000 zł net + 1,150 zł VAT = 6,150 zł gross
After correction: 4,500 zł net + 1,035 zł VAT = 5,535 zł gross
Difference: -500 zł net, -115 zł VAT, -615 zł gross
Correction and VAT
Seller:
- Reducing credit note (discount, return): you reduce output VAT in the period the credit note is issued
- Increasing credit note (error in the buyer's favor): you increase output VAT
Buyer:
- Reducing credit note: you reduce input VAT
- Increasing credit note: you increase input VAT
Correction in the National E-Invoicing System (KSeF)
From 2027 onward (for small/micro businesses), corrections in the national e-invoicing system (KSeF):
- A correction is a separate document in KSeF, linked to the original invoice
- The KSeF correction number is generated automatically
- The correction must reference the original's KSeF number
Most Common Mistakes
1. Issuing a Duplicate Instead of a Correction
Duplicate = identical amounts. Correction = changed amounts.
2. Missing Linkage to the Original
A correction must reference the original's number. Without it, the tax office (US) may reject it.
3. Storno Without a Reason
Storno zeroes an invoice — but you must have justification (non-payment, error).
4. Not Adjusting VAT After a Correction
If you issued a reducing credit note — reduce VAT in the declaration. Many forget.
5. Correction With a Different Sale Date
The sale date on the correction = the original's sale date. Not the credit note issue date.
FAQ
Can I issue a correction after a year?
Yes. There is no deadline. But the VAT correction affects the declaration for the period in which the credit note was issued.
Does a correction need to be signed?
Not since 2020. But recommended — especially for discounts and returns.
Is storno legal?
Yes, but it must have a reason (non-payment, error). "I just want to cancel" is not enough.
Is a correction in the national e-invoicing system (KSeF) different?
Yes — linked to the original via the KSeF number. Amounts are the same.
Need Help with Corrections?
I run sole proprietorship (JDG) accounting with full invoice handling — corrections, credit notes, storno, and the national e-invoicing system (KSeF). From 49 zł + VAT per month.
Reply to [email protected] or visit oxyok.com/pl.
Note: A correcting invoice (credit note) changes the original's amounts. It is linked to the original by number. It affects VAT in the period of issue. Before making a decision, consult an accountant.
Questions about accounting?
I run accounting for sole proprietors from 49 zł + VAT per month.
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