Record customer authorization
On a Work Order you can record how the customer authorized the work, so there is a record of why you were cleared to do it. If the customer is there, you can capture their signature. If they cannot sign, you can record that they authorized the work verbally. A signature is only accepted with the signature itself, and a verbal authorization never carries one.
The same step is used to record the customer's acceptance of the finished work, which answers a different question from authorization. Authorization says the customer agreed to the work being done. Acceptance says the customer accepted the completed work. Acceptance can only be recorded for a completed Work Order.
Each can be recorded once on a Work Order. If the work changes scope later, Change Orders handle the added work.