Nope, none - All it requires is your mobile number and email address.

The email is only to send you a receipt, so you could just create a random account for that if you don't want to use your normal email address.

You could also use a random email generator like Yopmail or something. Just keep in mind that if you do use a website such as Yopmail, the receipt that is sent to the "random email" includes your personal phone number - you also won't have a receipt should something go wrong with your Bitrefill transaction.