Quick definition The uptick rule restricts short sales to transactions where the price is moving higher than the previous trade price. In US equities, a short sale can only occur on an uptick or a zero-uptick (same price as the previous uptick). What it is The uptick rule is a simple circuit breaker on short selling. If a stock traded at 100 dollars and then 99.50 dollars, you cannot short at 99.50 (downtick). You must wait for a trade at 100 dollars or higher before shorting again. The rule is based on the idea that short sellers can pile on during downturns and drive prices lower artificially. The uptick requirement prevents this cascade. Why it matters Short sellers can influence prices downward by aggressively shorting. The uptick rule prevents them from shorting into falling prices, which would accelerate declines. This rule is thought to stabilise markets during crashes. The uptick rule was removed in 2007, then reinstated in 2010 after the financial crisis. Debate continues about whether it is effective. Alternative uptick rule After 2010, the SEC introduced the "Alternative Uptick Rule" (Rule 201), which applies only to stocks when they have declined 10 percent from their previous day's close. When this threshold is hit, the uptick rule is activated. It lasts until the next day's open. Practical example A stock declines 15 percent during the day, triggering the Alternative Uptick Rule. Short sellers are now subject to the uptick rule: they can only short if the price is moving higher. The stock has traded at 80, 79, 79.50, 80 dollars. A short seller can sell short at 80 (uptick from the previous price of 79.50) but not at 79 or 79.50 (downticks). Effectiveness debate Some argue the uptick rule is effective at preventing cascades. Others argue it is a minor impediment that does not significantly affect short selling or prices. The debate remains unresolved. See also - Short Sale - Regulation SHO - Short Squeeze - Circuit Breaker
