In August, Starbucks invested $25 million in Square and announced plans to let people use Square's app to pay in stores.

With Square Wallet people can pay at Starbucks and explore nearby businesses, browse menu information, store hours and transaction history, all on their phone.

To use the Square Wallet, customers tap 'pay here' and scan their QR code - similar to the customer experience on the existing Starbucks mobile payment applications. Their digital receipt appears instantly.

More innovative Square appliances, such as the 'pay by name' feature, are not included in the initial roll-out.

Square Wallet is in addition to Starbucks own mobile payment applications on iOS and Android, which the coffee chain says is used more than two million times each week.