盈透證券的Reg-T和portfolio margin

sec2100

In addition to the cash examples above, buying power may be provided to securities held in the margin account, with the leverage dependent upon the loan value of the securities and the amount of funds, if any, borrowed to purchase them. Take, for example, an account which holds $10,000 in securities which are fully paid (i.e., no margin loan). Using the Reg. T initial margin requirement of 50%, these securities would have a loan value of $5,000 (= $10,000 * (1 - .50)) which, using that same initial requirement providing buying power of 2:1, could be applied to purchase and hold overnight an additional $10,000 of securities. Similarly, an account holding $10,000 in securities and a $1,000 margin loan (i.e., net liquidating equity of $9,000), has a remaining equity loan value of $4,000 which could be applied to purchase and hold overnight an additional $8,000 of securities. The same principals would hold true in a Portfolio Margin account, albeit with a potentially different level of buying power.