Once you've sent out an invoice to a client, changing anything on your end could cause miscalculations and mismatched account information, which is why we do not recommend editing an invoice. However, there can be situations that you run into at times that require such an action to be taken.
Since there is no direct way to modify an invoice once it has been created, you can try the following workaround:
*Note down the invoice number for the invoice you wish to modify.
Choose Billings > Preferences and select Numbering.
In the "Next invoice" field, under Number, enter the invoice number you have noted down. This tells Billings to use this number for the next invoice that is being created.
Then click on the general pane-> and click on reset warning
- Delete the invoice you wish to modify. When prompted, click "Restore Slips."
- Go to the slips that were restored, make the necessary changes, and then re-create the invoice.