[stevejones]

The big deal in the UK, a few years ago, was that a person would go overdrawn, deposit money to cover it immediately but then get charged an overdraft fee by an overnight process. This fee would put them overdrawn, leaving them liable for a second overdraft fee - which would be charged the next night...

This was ruled to be illegal and banks had to set up whole departments to process return claims. I suspect this is the main cause of the big headwind.

[spjwebster]

It was slightly more insidious than that - they were processing debits before credits, and charging a fee for insufficient funds if your balance dipped below zero (or below your overdraft limit) in the process:

https://www.fca.org.uk/news/commitment-high-street-banks-ret...

[eru]

Also, when you had a bunch of outgoing positions a day, they (used to?) ordered them from biggest to smallest, thus hitting you with the maximum number of overdrawn transactions.

They also charged a fee for standing orders that didn't go through because of limited funds in your account. Instead of just ignoring them.