If invoices require the signature of the Service Provider, each provider can upload a signature image in their profile. 

From Service Providers in the main side menu, go to the "Invoicing" section of the provider profile to upload the Service Provider Invoice Signature. Image must be at least 350 pixels wide. Maximum image size is 5MB. Must be jpg, gif or png. Transparent backgrounds will not display properly.

You can also choose to Always Display the signature by default by selecting that option. 

To add or remove your signature on an invoice manually, you can toggle the “Add Signature” option at the bottom of the invoice.

An invoice can be accessed from 3 place, the Search Appointments tab, the Admin Calendar when viewing/editing appointment details, or you can search in the Finance > Invoices page.