As a rule, receipts are emailed to you by Google soon after the transaction is completed. However, purchases may be bundled together if you have made multiple purchases, and getting the receipt may take a bit longer. You can check your purchase history by following these steps:
- Go to http://payments.google.com and log in with your Google account
- Select Activity to display your Play Store order history
- Choose an individual entry to view its corresponding receipt
All purchases are processed by Google through Google Play for Android devices. If you have any issues with billing or questions about the billing process, you can contact Google here: https://support.google.com/googleplay