Sales Receipt

How can I provide a sales receipt to someone who made a payment to submit a form? 

Yes, this is possible. You would need to have an email field on your form that asks for the users email. Once you add one, it will automatically add an autoresponder to your email settings.

You need to edit your autoresponder template using this guide:

How to Strip Payment Labels and Separate Payment Info on Email Alerts 

Then your customers will receive an email with a receipt of their purchase on submission of your form.