You can keep track of your spending history by tapping on the Activity icon in the navigation bar at the bottom of the screen. This is also where all your receipts are chronologically stored.
To export a receipt, select the relevant receipt and tap on the Download icon next to the invoice number. The available formats for your receipts are PDF or CSV. After you will select the format you want, you will be able to send the receipt by email, text, or even print it.