To cancel a sent invoice:

1. Open the invoice from your invoice list
2. In the sidebar, scroll to the "Danger Zone" section
3. Click "Mark as Canceled"
4. The invoice status changes to Canceled

If the invoice is already paid or partially paid, open the original invoice and use "Create credit note / correction" instead.

Tip: Canceling keeps the invoice number in your records; deleting is only possible while a document is still a draft without a number.