How can I send a receipt to my registrants?

I have integrated Auth.net and have multiple email address fields in my form (allowing for multiple registrants for an event on one form, with one person entering payment info.) 

Authorize.net needs to email the receipt- so how do I know which address/ registrant is going to receive it? 

I just got a message from a registrant that no one received a receipt, so I'm a little perplexed.

Thanks.

You can create an autoresponder in your form to let your users know their transaction has been completed. You can see how to do this here: http://www.jotform.com/help/26-Creating-a-Form-Autoresponder 

Let us know if this helps.

I understand that I can email that it has been completed, but there's no way to set up the autoresponder to include the dollar amount paid and to which card, so it's not actually a receipt. 

That''s why I'm wondering about which email address authorize.net would send their receipt to when there are multiple email fields on the form. Can you advise?

You can add an email field in the just before the card details section and set it as required,

make sure the label reads as E-Mail this will be picked up by authorize.net and a receipt will be sent to that email address