How do I correct an invoice that has already been sent?

If the invoice was sent to the customer:

then the system no longer allows corrections to be made in the account:

1. Select Account View -Actions - Mark as Canceled:

2. When the account becomes canceled, then the system allows corrections to be made in the account:

3. After making the corrections, save the changes and select again in the bill viewActionsbutton and cancel account cancellation: