Deleting or modifying an invoice is illegal! Nevertheless, there are solutions to correct an invoice.
Consists in cancelling the “erroneous” invoice, provided that an invoice containing the “negative” of this invoice is also issued.
To learn more visit: How to cancel an invoice?
Attention! This action is only possible if the invoice is in “Payment Due”. If a payment has already taken place then you can no longer cancel it.
2/ The refund
If the invoice has already been honoured, you still have the option to refund it.
To learn more, visit: How to refund an invoice ?
3/ Adding a line of credit.
Finally, if you do not want to reimburse the entire bill or for some other reason, you want to make a commercial gesture that will apply to future bills. You can add a line of credit to the customer’s balance.
To learn more visit: How to add a line of credit/debit in the customer’s balance ?