Why did I receive a margin call when the market didn't move much?

Margin calls are based on the risk level of the positions in your account, not necessarily the actual market changes on a given day. Margin requirements may change without notice based on factors including:

Volatility of securities you are holding - More volatile stocks have higher requirements
Industry and sector risks - Requirements vary based on the risks of different industries
Trading volume in your account - Active trading may result in higher requirements
Options positions - Writing or holding options results in incremental margin needs
Overconcentration in one stock or sector - Concentrated risk may mean higher requirements
Redbridge's discretionary determination - We may increase at any time based on our discretion

Even a small decrease in account equity can trigger a call if these variables result in requirements in excess of your maintenance excess. We issue margin calls to ensure your positions remain properly collateralized based on the total current day risk, not just daily market changes.