Short options
How does Margin Interest and Buying Power Reduction (BPR) affect the return on capital of short options?
By Easy Money Scanner · Educational reference · Not investment advice
The short answer
Margin interest and buying power reduction lower the effective return on capital for short option strategies, since brokers hold a portion of account equity as collateral, meaning the actual annualized yield is typically lower than the premium collected compared to total capital.
How it works
Return-on-capital calculations for short premium trades should factor in BPR rather than just premium received, since two trades with identical premiums can have very different capital efficiency based on BPR.
An example
A $500 premium collected against a $5,000 buying power reduction yields a 10% return on capital, while the same premium against $2,000 BPR yields a 25% return.
Risk & limitations
Cboe and broker margin rules note BPR can change intraday based on volatility and price movement, altering available capital and existing position risk calculations.
Examples are hypothetical, not trade recommendations. US contract and regulatory references do not automatically apply in Canada. Rules, margin requirements and broker policies can change; confirm them with the relevant authority and your broker.