My IB account overnight cash balance was -3,269.38 on August 29, based on the daily account information, I was charged $1.25 for interest, which means the anual percentage rate is over 10%. I traded ES daily but closed all future position before 4pm, and only hold stock long position over night. I am wondering if the interest rate is really so high now?
calculation examples are here: http://www.interactivebrokers.com/en/accounts/fees/interestMethods.php#examples the rate charged was probably around 7.15% (libor +1.5%) I'm guessing but it looks like you have been charged 2 days interest. Is it possible you were short cash over the settlement period?