The self-invite feature is designed specifically for the situation where you do not know your customer’s email address; examples are: in a restaurant, health farm, vehicle and tool hire, and most stores / shops.
Below are special questions that integrate your survey responses into our response invite system - we call it a "self-invite".
The point here is to record the response next to a unique ID (invoice number), so you can track and / or chase the feedback. In addition, the email confirmation question will force your responder to confirm their email address before they proceed.