To see your purchase history, do the following:
Android:
1. Go to the payments.google.com, then sign in to the correct Google account;
2. Select Transactions to view the order history in the Play Store;
3. Select a specific entry to view the invoice.
iOS:
1. Open iTunes on your computer;
2. Select the username (e-mail address) and Account;
3. Scroll down to the Purchase History and click View All.