Retain customer email address
As a customer it is annoying to have to enter my email address with every transaction. Square is able to retain a customer's email address (presumably tied to credit card).
Gary Hooper commented
I am a customer using a merchant's terminal. I need to enter my email address for each transaction.
Instead, please retain my email address, associating it with my credit card number. Then, after my first purchase, you could confirm that I want to use what I previously entered, rather than requiring me to re-enter it each time. This will save much time for both the merchant and the customer.