Billing Settings is where changes can be made regarding sales tax, transaction notifcation emails as well telling you whether you can accept credit cards or ACH payments. To get to the Billing Settings from the Home page click on the Billing tab in the far left top menu, then click on Billing Settings on the right side menu.
Below is an image of what the Billing Settings page looks like. If you accept Credit Cards, the check box will be checked, if not it won't be. If you accept ACH, the box next to Check will be checked.
You have the option to turn on email notifications to the students for a receipt as well as if their transaction fails. Make sure there is an email in the student profile otherwise no email will be sent out.
After any changes are made, make sure to click the Update Billing Settings button at the bottom to save your new changes.