Right in your profile! Well, almost... Look here!
All of your subscriptions, current and prior, are located in your subscription page. To get there, go to your profile page, click the little cog wheel in the upper right, next to your profile icon and name (1.)
and then "My subscription". (2.)
Now your current subscription is displayed at the top and click "View receipts" at the bottom of the page for your receipts (3.)