The Current Account Switch Service (CASS)

An obvious hurdle to CASS is Merchants & Banks Who Don't Yet Recognise the Monzo Current Account Sort Code / Debit Card (open Wiki)

There are plenty of large companies there basically saying that they refuse the believe monzo even exists… how would they handle a CASS request? They’d more likely just bounce it, causing pushback to monzo as it’d be seen as their fault.