Sprout Invoices now has the ability to require a digital signature from your clients before they can pay a WordPress invoice or accept an estimate.
It’s a simple plugin that adds a signature area below your invoices and estimates terms section. Below is an example of the plugin in action.
A Client Digitally Signing an Invoice before Payment
Admin can disable this per invoice or estimate, as shown below.
The signature is saved within the history for the document, as shown below.