> What about funded accounts with no clearance in progress?

Other comments have already mentioned that they can't use customer funds for the deposit, so they need to pay it out-of-pocket or borrow it.

I think this is only the case when the customer has sold something and immediately buys before clearance. I'm speaking about the standard case where you purchase stocks with funds in your account -- does that also require a deposit from the broker?

The stock trade still takes two days to settle. Apparently this is to allow for correcting errors before it becomes irreversible.