4x see http://www.interactivebrokers.com/html/retailAccount/stock_margin.html (most is pasted below) Patterned Day Trader Margin Requirements The NYSE and NASD have imposed rules to limit small investor Day Trading on US stocks. Customers who have made four or more US stock or option day trades (open and close a position on the same security in a single day) within five business days in their account are considered "Patterned Day Traders". "Patterned Day Traders" are required to hold a minimum of $25,000 in "Equity with Loan Value", and therefore those customers without this minimum "Equity with Loan Value" and who have completed three day trades within five business days will not be allowed to enter another trade. This restriction will remain in effect until five business days from the first day trade have elapsed. The Day Trading margin requirements are in effect from 9:30am to 3:55pm NYT each trading day, and at 3:55pm each trading day regular stock margin requirements will govern until the opening of the next trading day. "Patterned Day Trading" margin requirements are as follows: Initial and Maintenance Purchase: maximum (25% * marginable stock value, $25,000) or maximum (100% * non-marginable stock value, $2,000). Short sale: if last sale price/share >= $17 then maximum (25% * marginable stock value, $2,000), else if $17 > last sale price/share > $5 then maximum ($5 * marginable shares, $2,000), else if last sale price < = $5 then maximum (maximum (marginable market value, $2.50 * marginable shares), $2,000) or maximum (100% * non-marginable stock value, $2,000). Short sale proceeds are applied to cash and the short position is subtracted from equity.