For your customer to receive an automated receipt for successful transactions, you will need to go to your Authorize.Net account settings.  

Go to: and Login to your account > From the Home Page > Account > Settings > Transaction Format Settings > Email Receipt > Enable Email Confirmation > Check 'Email Transaction Receipt to Customer'  

*Please be sure that you have the correct email address on file for the client.  If you want your EzSchedule/ARB customers to receive email receipts as well, be sure to click on the checkbox next to 'Email Customer for each Successfully Authorized ARB Transaction'