Correct. And more to the point, RH cannot use customer funds to cover that timeframe.

It must be its own funds. And the requirement of funds to be covering (collateral) can change on them with very little warning

Who determines the collateral required?

The NSCC sets the framework, but it is spelled out in Dodd-Frank that they have to do so by law.

There are some other items, but that's the basic idea - full details are here: https://dtcc.com/-/media/Files/Downloads/legal/policy-and-co...

If you want to dive further i recommend this thread :

https://mobile.twitter.com/KralcTrebor/status/13549526861652...

It’s federal law, part of the Dodd-Frank reforms in the wake of the 2008 financial crisis. I recommend this: https://twitter.com/kralctrebor/status/1354952686165225478?s...

I only knows how it works in otc derivatives and then the collateral is equal to the cost of taking an offsetting position, and is calculated inter-day. But I would guess it is something similar on the stock market.

In this case, the NSCC, or the NAtional Securities Clearing Corporation.

This is the right answer. And with the amount of volitility GME was seeing, and the amount of trades of it, created lots of money for the user, but RH was still days away from the transactions actually settling, thus they didnt have the cash from the sale yet.