Plus/minus corrections, the agreement-of-conditions mechanism in KSeF, and most common mistakes — practical guide by Danexis.
With KSeF mandatory in 2026, the way you issue corrective invoices changes. KSeF number, date of receipt and the agreement mechanism are new concepts every entrepreneur must master.
Issue when reducing net amount, VAT, or granting a discount/refund. In KSeF the agreement date is the date the buyer receives the correction in the system — email documentation is no longer needed.
Issue when raising the price, adding items or correcting a VAT rate to a higher one. Settled in the period of issuing the correction unless the error existed from the start.
The KSeF number of the corrected invoice must appear on the correction — the system maintains the link automatically. 'Manual' corrections outside KSeF are not recognised (exceptions: VAT-RR, consumers).
1) Wrong KSeF identifier. 2) Wrong settlement period. 3) Missing advance correction before the final one. 4) Issuing a zero correction instead of cancelling — an invoice in KSeF can only be corrected to zero.
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