EVERY clearing broker monitors risk to some extent during the day, based on their WSP. This does not go away with large accounts and that is not why firms like IB have a auto-liquidation policy to protect against margin calls. I went over that in the post above. Risk and margin are two different issues. Risk policies are always more stringent or equal to margin. I believe, but have to confirm, that accounts with equity over $5mm, the clearing firm does not have to calculate Day trading requirements through time and tick, but for accounts under $5mm, they do. They still can if that is their policy. The OCC does not calculate PM on your position until after the close. You clearing firm can only estimate that value during the day. And, the OCC looks at EOD positions only for your PM requirement. However, since all clearing firms have higher requirements than the OCC, it does not matter.