You can cancel an invoice by issuing a credit note.
To create a credit note, follow these steps:
Open the original invoice from the invoice list
Click on the 3 dots (top right)
Select "Create" > "Credit Note"
If necessary, edit the information in your credit note. A credit note will automatically register the total amount of the invoice, so make changes if you only want to issue a credit note for a partial amount.
You should also write the reason for the cancellation in the "Notes" section.
When you’re ready, click the blue "Complete" button.
If a payment has already been connected to the invoice, you must first remove the payment in order to create a credit note directly from the invoice. To do so, open the invoice, scroll down to the history section, and click "Delete" next to the payment. You can then proceed as described above.