Ah, thanks. To be honest, in the UK in my experience the "within a few hours" thing only seems to apply when the transfers are between accounts at the same bank.

Transfers to other banks are the same process, they just take days; especially if it's a weekend or a public holiday. I'm sure all of that's just an excuse to hang on to your money for as long as they can.

Actually, the faster payments system make interbank transfers (for member banks) go within minutes, and intrabank transfers shouldn't take more than a few seconds.

That, at least, is my most recent uk banking experience...

"Within same bank" transfers in the U.S. usually happen by end-of-same-business-day, sometimes within minutes.

I always figured that the 3-business-day wait was because of the interbank settlement process. Banks settle up at midnight between each business day: at that point, there's a shuffle where they figure out how much capital they need to meet reserve ratio requirements after the day's deposits & withdrawals, borrow from other banks at the Fed funds rate, or in the worst case, borrow from the Fed's discount window. If you figure a business day to transfer the money internally, then a business day to settle up with counterparties, then a business day for the money to appear in the receiving account, there's your 3 days.

(I suspect they also pad the times a bit...when I've transferred money, it's usually taken a day and a half to two days for it to appear, which is consistent with the intraday settlement process. They want a little bit of a cushion in case some employee isn't on the ball or things otherwise get hung up.)