Cancel or correct an invoice

Open the finalized invoice. The Invoice history section shows only the actions that are possible for it right now.
Invoice not yet sent or paid: choose Void, optionally write a Reason (optional) and confirm with Void for good. The number stays taken and the booking is reversed.
Invoice already sent: choose Cancel and then Issue cancellation invoice. A cancellation invoice with its own number cancels the full amount. The original invoice stays unchanged.
Only part of the invoice is wrong: choose Corrective invoice. Fill in Description, Credit (gross) and VAT, then choose Create correction draft.
The correction opens as a draft. Check it and finalize it like any other invoice.
Cancel is no longer available once a corrective invoice exists. To issue the invoice again correctly, use Copy, which makes a new draft from it. Invoice history lists every cancellation and correction.