What Is the Uptick Rule and When Does It Restrict Shorting?

“Why won’t my short fill at the bid?” On a day when a stock has dropped sharply, the answer is often a price test the SEC wrote into Regulation SHO, known as Rule 201 and loosely called the uptick rule. Many platforms flag it as SSR, for short sale restriction.

The trigger is a fall of 10 percent or more from the prior close. Once that happens, the restriction applies for the rest of the trading day and for the whole of the following day, and while it is in force, short sales can only be executed at a price above the current national best bid.

Some history. The original uptick rule was removed in 2007. The SEC adopted Rule 201 in 2010.

Working out the trigger price

The sum is short. Multiply the prior close by 0.90.

Do the calculation before the open on any stock you plan to short. If the stock opens at 39.00 on bad news, it sits 0.75 above the trigger, and a small further slide flips the restriction on, which can change how your order fills halfway through the move you were trying to catch.

How long it lasts

Once triggered, it stays on. A bounce back above 38.25 does not switch it off, and a rally all the way back to the prior close leaves it in place too, because the rule cares only that the trigger was hit.

Say the stock closes Monday at 42.50 and first trades at 38.25 around 11:00 on Tuesday. The restriction runs from that moment through Tuesday’s close and all of Wednesday. It lifts after Wednesday unless the stock triggers it again, which would take a fall of 10 percent or more below Tuesday’s close during Wednesday’s session, starting a fresh period that runs through Thursday.

Each new test measures from the latest close. The trigger price moves every day.

What “above the national best bid” means for a fill

The national best bid is the highest displayed bid across US exchanges. Normally a short seller can sell straight into the bid. Rule 201 takes that away.

Say the quote reads 37.90 bid, 37.95 offer, and the restriction is active.

• A short sale at 37.90 is not allowed.
• A short sale at 37.91 or higher can execute.
• In practice, you post an offer and wait.

That changes what kind of trader you are on that stock. You are now passive. You rest on the offer side and rely on buyers coming to your price. In a stock that keeps falling, buyers may not come, and your order can sit unfilled while the bid drops away from it, so the restriction bites hardest in exactly the conditions that tempted you to short.

Market orders to sell short clash with the rule. A market order would hit the bid. How brokers handle them varies. Some reject them while the restriction is active. Some convert or reprice them. Check your broker’s order-handling notes for short sales.

What the rule leaves alone

Covering is unrestricted. Buying to close a short is a purchase, and Rule 201 is a limit on short sales only, so a stop on an existing short can still trigger and buy you back. Placing one is covered in setting a stop on a short position.

Long sales are also untouched. If you own shares and sell them, the price test does not apply.

Existing shorts are left alone as well. A position you opened before the trigger stays open, with nothing forcing you out of it, since the rule governs only new short sales while it is active. Adding to that position is a new short sale, though, so the price test applies to it.

Where it shows up on your platform

Most platforms mark a restricted stock on the quote or order ticket, often with an SSR label or a warning when you choose to sell short. If yours does not, do the multiplication yourself.

Rule 201 is one of several frictions on the short side. Borrow cost is another, and a stock that has just fallen 10 percent in a day can also be hard to borrow, which means you may be posting above the bid on a position that charges you a fee for each day you hold it.