Yes, when you have completed the payment, you will be given the opportunity to request a receipt or a VAT receipt. You will need to enter a valid email address and click on send. The receipt will have a transaction number that you can quote in the event of a query.
If you forget to request for a receipt at the time of payment, or you have deleted the email you can call Customer Services who can reissue the receipt. However, you will need the date you made the payment, the account/invoice number you quoted, and the amount paid. If you are unable to provide this information, then Customer Services will not be able to find the payment to reissue the receipt.