Assuming you maintain a margin account with IB LLC, the buying power of any given stock is a function of its characteristics, subject to regulatory minimum margin requirements. Characteristics considered include factors such as its listing, liquidity, volatility and market cap.
U.S. regulations require minimum initial and maintenance margin requirements for Reg. T accounts of 50% and 25%, respectively. This translates to overnight and intraday buying power of 2:1 and 4:1, respectively. In a Portfolio Margin account, the regulatory minimum is 15% which translates to buying power of 6.67:1 (note that IBKR imposes house requirements which afford that level of buying power to portfolios which are well diversified and comprised of low volatility securities).
In addition, there are certain classes of securities which are subject to a 100% margin requirement and offer no buying power. They include the following:
- PINK sheet listings
- OTCBB listings
- Venture Exchange listings
- Small cap stocks (market cap below $250 million)
- Canadian listings with a share price below CAD 2
- Pharma/Biotech stocks with a market cap below $5 billion
- Non-U.S. stocks classified by FINRA as having No Ready Market: