UK banks work to an expectation of 0-3% margin. In Monzo's favour is that they don't have to operate a branch network, but then again they are small compared to

UK banks work to an expectation of 0-3% margin. In Monzo's favour is that they don't have to operate a branch network, but then again they are small compared to the high street banks. There's just not a lot of money available in accounts, even accounting for using it for lending etc. Also bear in mind that while they can use deposits to fund some amount of lending, the amount they have to keep on hand, collateral, insurance (not sure if it's called that) with the Bank of England, etc, are all very heavily regulated so that they can't mess it up, which conversely means it's much harder to monetise than expected based on a basic understanding of fractional reserve banking.