What is the Uptick Rule? Definition, Formula, and Example
The uptick rule is a regulation that restricts short selling in a stock that has fallen 10% in a day, allowing new short sales only at prices above the current best bid.
What is the Uptick Rule?
The uptick rule is a Securities and Exchange Commission restriction on short selling designed to prevent short sellers from piling onto a crashing stock and accelerating its decline. The modern version, Rule 201 of Regulation SHO (adopted 2010), is triggered when a stock's price drops 10% or more from the prior day's closing price. Once triggered, short sales may only be executed at a price above the current national best bid — effectively, shorts can only sell into buyers lifting offers, not hit bids. The restriction stays in effect for the rest of that trading day and the entire following trading day.
How the Rule Works
The mechanics are deterministic:
1. Trigger: intraday last-sale price ≤ 90% of the prior day's official close.
2. Restriction: short sale orders must be priced at least one tick above the NBB (national best bid). Marketable short market orders are rejected or converted.
3. Duration: remainder of the trigger day plus the next full trading session.
4. Scope: applies to all exchanges, dark pools, and off-exchange venues; market makers with bona fide hedging activity receive limited exemptions.
The original 1938 uptick rule (Rule 10a-1) required every short sale to occur on an uptick or zero-plus tick, at all times, in all stocks. The SEC repealed it in 2007 after pilot studies showed minimal effect on liquid stocks — then reinstated the circuit-breaker version in 2010 after the 2008 crisis.
Worked Example
Suppose XYZ closed yesterday at $50.00. Today it sells off on a downgrade:
- Trigger price: $50.00 × 0.90 = $45.00
- At 11:20 a.m., a print hits at $44.98 → Rule 201 activates immediately.
- From that moment, with the NBBO at $44.90 × $44.92, a short seller may only execute at $44.91 or higher — they cannot hit the $44.90 bid.
- The restriction remains active through the close of the next trading day, even if the stock rebounds to $49.
Traders see this on Level 2 as the "SSR" (short sale restriction) flag on the ticker.
When Traders Use It
- Short-side traders must adjust execution: limit orders pegged above the bid, or wait for upticks, which worsens fill rates and slippage on entries.
- Long traders watch SSR names for squeezes: restricted shorting removes a source of sell pressure, and crowded shorts unable to add can become forced buyers.
- Day traders screen for SSR-flagged stocks because the rule mechanically changes order-flow dynamics for two full sessions.
Limitations and Common Misconceptions
The rule does not prevent declines — stocks under SSR routinely fall another 20%+; it only slows the *mechanical* contribution of short selling. It does not apply to market makers' hedging flows, options market makers can still create synthetic short exposure, and put buying is unrestricted. It is also frequently confused with the older always-on 10a-1 rule, which no longer exists. Finally, the 10% trigger is measured against the prior *close*, not the day's open, so a stock that gaps down 9.9% and bleeds further never triggers it.