Edit Completed Service Order
If you delete the invoice you can go back and edit the order then re-invoice it.
1) Go to Income -> Invoices.
2) Search, and then click the invoice number to edit.
3) Click on the "Edit" button.
4) At the top of the page, click on "Unpost".
If a payment has been applied you will first need to void the payment by going to Income -> Payments -> Void Payments. Then return to step 1.
5) At the top of the invoice edit page, click "Delete".
6) Go to Income -> Orders, and select the order to edit.
After you edit the order, you can re-invoice it with your changes.