Can a receipt be given once a person completes the form?

You may set up an Autoresponder email which will be sent to the user who submits the form.
Then you can edit the email template of the Autoresponder and make it look like an invoice.

Here are two guides that will help you achieve that:

Setting up an Autoresponder Email

How to Edit the Email Template for Notifications and Autoresponders

You may also strip your products labels and add them in your autoresponder.

Guide:How-to-Strip-Payment-Labels-and-Separate-Payment-Info-on-Email-Alerts

Please give it a try and let us know if this fits your requirements.