What is an acceptable proof of purchase?

A receipt is perfect. If you don't have it then a bank or credit card statement showing the transaction is fine.

If it was a cash purchase in Store and you don't have a receipt then get in touch with us here and we may be able to help you with the proof of purchase. To do this we'll need the date and the exact amount it was for. Without that, we won't be able to help, unfortunately.