Where can I find my payment receipts?

Open iTunes.
If you’re not signed in, sign in with your Apple ID.
From the menu bar at the top of your computer screen or at the top of the iTunes window, choose Account >> View My Account.
On the Account Information page scroll down to Purchase History. To the right of Most Recent Purchase, tap See All. It might take a moment for your Purchase History to appear.
To see the details of a purchase, tap the arrow to the left of the order date. Your most recent purchases are first.

You must have also received an email with each receipt.