Uptick rule

The uptick rule is a trading restriction that states that short selling a stock is only allowed on an uptick. For the rule to be satisfied, the short must be either at a price above the last traded price of the security, or at the last traded price when the most recent movement between traded prices was upward (i.e. the security has traded below the last-traded price more recently than above that price).

The U.S. Securities and Exchange Commission (SEC) defined the rule, and summarized it: "Rule 10a-1(a)(1) provided that, subject to certain exceptions, a listed security may be sold short (A) at a price above the price at which the immediately preceding sale was effected (plus tick), or (B) at the last sale price if it is higher than the last different price (zero-plus tick). Short sales were not permitted on minus ticks or zero-minus ticks, subject to narrow exceptions."

The rule went into effect in 1938 and was removed when Rule 201 Regulation SHO became effective in 2007. In 2009, the reintroduction of the uptick rule was widely debated, and proposals for a form of its reintroduction by the SEC went into a public comment period on 2009-04-08. A modified form of the rule was adopted on 2010-02-24.