I've been thinking about this recently. With the T+3 system, all my trades made on a single day are settled at the same time 3 days later.
Say hypothetically, i bought stock $100K of stock XXX on open, and sold an hour later getting $102K, this trade would be settled 3 days later and my account would just be credited 2K right? So what i'm trying to find out is if I could make this trade without having the $100K in the first place - say I only had $20K. I know this is risky, but considering the massive increases during open of alot of resource stocks this week... i think its possible to reap a few K profits.
I do realise the risk involved if the price moved the opposite direction, but is this possible???