Verifying Receipts

According to Apple - Delivering Products:

The app receipt contains a record of the user’s purchases, cryptographically signed by Apple. For more information, see Receipt Validation Programming Guide.

Information about consumable products is added to the receipt when they’re paid for and remains in the receipt until you finish the transaction. After you finish the transaction, this information is removed the next time the receipt is updated—for example, the next time the user makes a purchase.

Information about all other kinds of purchases is added to the receipt when they’re paid for and remains in the receipt indefinitely.

When an app is first installed, the app receipt is missing.

As soon as a user completes a purchase or restores purchases, StoreKit creates and stores the receipt locally as a file, located by Bundle.main.appStoreReceiptURL.