It never used to be that way, but it might be now, I know theyre alot stricter for capital than they used to be.
It used to work that trades acted as if the unsettled balance was the sum of all comings and goings on a T+2 basis, thus you could keep trading as long as the total net outgoings never exceeded the capital in your account (which would mean you traded very badly or hadn't sold a position in 2 days).
