This is exactly what the beautiful retards over at WSB were doing to robinhood called it "infinite leverage". Dudes putting up $2k of their own money shorting stocks over and over until they have $50k in their account to blow on OTM AAPL puts...
below is the reply from IB staff: --------------------------------------------- Short stock collateral cash gets backed out from settled cash (along with futures risk margin) when arriving at the cash principal subject to interest. So the cash proceeds from short sales would debit against your settled cash. For example: Start with 1mm settled USD Short 1.5mm worth of SPY (assume collateral value for simplicity's sake) Cash = 2.5mm vs. Principal = (500k) So if you were to then buy, i.e. 500k worth of US-T, that amount gets backed out again. Cash = 2mm Principal = (1mm)
Well, unless they bought the Puts in October 2018 and sold them late December 2018 that didn’t work out at all.