[Google Play]

  1. On your mobile device, open the Google Play Store app Google Play.
  2. Tap Menu Menu and then Account.
  3. Tap Purchase history.
  1. Go to your Google Play account.
  2. Scroll down to review your orders.
  1. Go to pay.google.com.
  2. Find Other purchase activity.
  3. Select View purchases. 
  4. Select an order to see your receipt.

Source: https://support.google.com/googleplay/answer/2850369

[iOS App store]
- Open App Store > Tap the top right icon of the screen
- Select your account and login
- Select Purchase History