A pricing error, a discount granted after the sale, or a return of goods — in each of these situations the business owner must issue a correction invoice. Since 2026, with the entry into force of the mandatory National e-Invoicing System (KSeF), the rules for issuing and settling corrections have changed significantly: correction notes have been abolished, and settling downward corrections has become simpler than before. Here is how to correct invoices properly in a sole proprietorship.
When a correction invoice is issued
A correction invoice is always issued by the seller — whenever, after the original invoice was issued, the taxable base or the tax amount has changed, or the invoice contains an error. The Polish VAT Act lists in particular: granting a rebate or price reduction, the return of goods or packaging, the refund of all or part of a payment (for example an advance payment), a price increase, and a mistake in the price, tax rate, tax amount or any other item on the invoice. A correction is always issued in relation to a specific original invoice — it must reference that invoice's details and, for an e-invoice, also the identification number of the corrected invoice in KSeF.
The end of correction notes — only the seller can fix errors
Until the end of January 2026, minor formal errors, such as a typo in the buyer's name or address, could be corrected by the buyer themselves by issuing a correction note (nota korygująca). With the entry into force of mandatory KSeF, the provisions on correction notes were repealed. Since 1 February 2026, the only way to fix an error on an invoice — including a purely formal one — is a correction invoice issued by the seller. In practice, a buyer who spots a mistake should report it to the issuer as soon as possible and request a correction.
As a reminder of the timeline: from 1 February 2026 the obligation to issue invoices in KSeF covers companies whose sales for 2024 exceeded PLN 200 million, and from 1 April 2026 it covers all other businesses, including sole proprietorships. Importantly, correction invoices relating to original invoices issued outside the system in previous years are also issued in KSeF.
Downward corrections — simpler settlement than before
The biggest simplification concerns corrections that reduce the taxable base, known as downward (in minus) corrections — a rebate, a return of goods, or a refund of an advance payment. A seller who issues such a correction invoice in KSeF reduces the taxable base and output VAT in the return for the period in which the correction was issued. They no longer need to collect documentation confirming that the terms of the correction were agreed with the buyer, as the earlier rules required.
On the buyer's side the rule mirrors this: the buyer reduces input VAT in the return for the period in which they received the correction invoice. For an e-invoice, the date of receipt is deemed to be the day it was assigned its identification number in KSeF — as a result, both parties generally settle the correction in the same period, which limits discrepancies between the seller's and the buyer's records.
Upward corrections — the reason is decisive
For corrections that increase the taxable base (in plus), the reason for the correction is key. If it already existed when the original invoice was issued — for example the price or the VAT rate was understated by mistake — the correction is settled retrospectively, in the period in which the tax obligation from the original invoice arose, which often means amending a JPK file that has already been submitted. If, however, the reason arose later, for instance the parties agreed a price increase after the delivery, the correction is recognised on an ongoing basis, in the period in which that reason occurred.
Adjusting revenue and costs for income tax
A correction invoice affects not only VAT but also income tax. Here a separate rule applies: if the correction is caused by an arithmetic error or another obvious mistake, the revenue or cost is adjusted retrospectively — in the period in which it was originally reported. If the correction results from other reasons, such as a rebate or a return of goods, it is recognised on an ongoing basis: by the seller in the period the correction invoice was issued, and by the buyer in the period it was received. Entrepreneurs on the lump-sum tax on recorded revenue (ryczałt), who adjust revenue only, proceed in the same way.
What to keep in mind in practice
In KSeF it is not possible to cancel an issued e-invoice or delete it from the system — every error, even issuing an invoice to the wrong counterparty, requires a correction invoice, if necessary one correcting the amounts down to zero. It is therefore worth verifying the data before sending an invoice to the system and regularly reviewing purchase invoices, so that mistakes are caught quickly and the seller can be asked for a correction. Stating the reason for the correction is also good practice — although it is not a mandatory element of a correction invoice, it makes it easier to determine the right settlement period for VAT and income tax.