The Order History section of the Account Settings will show you your receipts when your MobileCause account renews. So if this is your first year with MobileCause, you will not see receipts. The first year receipt was sent to you through email when you signed up.
When you have been with MobileCause for more than a year, you will see the summary of the renewal payments and you will be able to download a PDF of the renewal receipt.
The Renewal receipt will look something like this: