How it works
The trader’s broker locates shares to borrow (usually from another client’s margin account). The shares are sold in the market, and proceeds sit as collateral. To close, the trader buys the shares back and returns them to the lender. The trader pays a borrow fee for the duration of the short, plus any dividends the borrowed shares pay. Hard-to-borrow names can carry borrow rates of 50 to 200 percent annualised.
Example
A trader shorts 100 shares of XYZ at $80. If XYZ falls to $60, closing the short captures $20 × 100 = $2,000 profit, minus borrow fees. If XYZ rises to $120, closing at $120 costs $40 × 100 = $4,000 loss, more than the original sale proceeds. If XYZ rises to $200 (think GameStop January 2021), losses on 100 shares = $12,000 on an $8,000 initial position. The asymmetry is fundamental: upside is capped at 100 percent, downside is unbounded.
Why it matters
Short selling adds price discovery and helps deflate bubbles, but carries unique risks. Short squeezes (sharp rallies triggered when shorts must cover) can be catastrophic. Borrow can be recalled (forced cover) at any time. Regulators occasionally ban short selling on specific names or sectors during stress, which removes the ability to manage risk. Most retail traders should use put options or inverse ETFs for downside exposure rather than naked short selling: the risk profile is bounded and operational complexity is lower.
