The best way to do that is to encourage the customer to go to the bottom of their receipt, and click the "Manage Preferences for digital receipts" option. From there, they'll be able to unsubscribe from automatic receipts from either all Square sellers, or just your business specifically. Here's help article that explains more: Automatic Receipts
As a side, if you would like to turn off automatic receipts for your business as a whole, let our Support team know, and they'll take care of it for you!
