Teller uses the APIs used by the bank's own mobile app, i.e. they have been reverse-engineered. Whether Teller requires personal credentials is dependent on the

Teller uses the APIs used by the bank's own mobile app, i.e. they have been reverse-engineered. Whether Teller requires personal credentials is dependent on the bank's implementation. Barclays (integration temporarily unavailable), and Nationwide use EMV CAP (the card reader) for registration. If we can figure out a way to not take user credentials, we will always take that route. I recommend Starling and Monzo if you want a read-only API for your own account, but if you want to build apps for 65 million customers they're not yet much use to you.