Just got an account at ThinkorSwim to start trading options and I have a few questions on settlement and margin. For right now I am simply going long calls/puts (100% margin requirement). Why is it that if I buy and sell a contract in the same day, it settles instantly? Why is it that if I sell a contract I held overnight, I can buy a contract but not sell it? The instant settlement is nice, basically like a prop shop. Im I missing something here? Ive only done one daytrade for the instant settlement as I have not fully funded the account yet, just a trial. Can I buy and sell all day as long as I don't hold overnight and don't go over the total cash value of the account? Will I be blocked from trading as I come to 2/4 times the cash value? Am I paying margin fee's for any of this? Thank you in advance.