To add an even clearer source to the other replies: https://www.interactivebrokers.com/en/index.php?f=1595 https://www.interactivebrokers.com/en/index.php?f=159

To add an even clearer source to the other replies: https://www.interactivebrokers.com/en/index.php?f=1595 https://www.interactivebrokers.com/en/index.php?f=1595 IB is abundantly clear that it makes money from cash balances. I'm not sure where you got this idea from.