Short Selling and Regulation SHO

Ask most people about short selling rules and they’ll tell you about the uptick rule: you can only sell short on an uptick, after the price has risen.

That rule was eliminated in 2007. It hasn’t existed for nearly twenty years.

What replaced it in 2010 works completely differently. Rule 201 of Regulation SHO is a circuit breaker: nothing restricts short selling at all until a stock falls 10% or more from the previous day’s close. Once that happens, short sales may only execute above the national best bid — for the rest of that day and all of the next.

No trigger, no restriction. Trigger, and a price test switches on. That’s a different mechanism from a tick test, and study material describing the old rule is describing something that no longer exists.

The short answer

A short sale is selling a security you don’t own, by borrowing it, hoping to buy it back cheaper. Profit if the price falls; loss if it rises.

It can only happen in a margin account. Never a cash account. This follows from the mechanics — you’re borrowing.

Losses are theoretically unlimited. A long position can only fall to zero. A short position loses money for as long as the stock keeps rising, with no ceiling.

Regulation SHO has four working parts:

Rule	What it does
200	Defines “long” and “short” and requires every sell order to be marked long, short, or short exempt
201	The circuit breaker. A 10% decline triggers a price test for the rest of the day and the next
203	The locate requirement — you must reasonably believe the security can be borrowed and delivered before selling short
204	Close-out — fails to deliver must be closed out on a deadline tied to settlement

Margin on a short position is 50% initial under Reg T and 30% maintenance — higher than the 25% for long positions, because the risk is unbounded.

The full answer

The mechanics

You borrow shares from your broker, sell them at the current price, and at some point buy them back and return them.

If the stock falls, you buy back cheaper and keep the difference. If it rises, you buy back at a higher price and absorb the loss.

Three consequences flow from the fact that you borrowed:

You owe the dividends. While you’re short, any dividend paid on the borrowed stock is your obligation to the lender. You didn’t own the shares on the record date — the lender did — so you make them whole.

You can be bought in. The lender can recall the shares. If your broker can’t find replacement stock to borrow, your position gets closed whether you wanted to exit or not. Short sellers don’t fully control their exit timing.

You pay to borrow. Hard-to-borrow securities carry meaningful borrow fees that accumulate against the position.

Why it must be a margin account

A cash account is exactly what it sounds like: you pay in full, you own what you bought. There’s no borrowing mechanism.

A short sale is borrowing by definition. Short sales must be executed in a margin account.

The margin requirements are stricter than for long positions:

	Long	Short
Initial (Reg T)	50%	50%
Maintenance	25%	30%
Minimum equity to open	$2,000	$2,000

The 25-versus-30 split is heavily tested and easy to reverse. The reasoning is straightforward: a long position’s worst case is the stock going to zero. A short position has no worst case, so the maintenance floor is set higher.

The unlimited loss problem

Buy a stock at $50 and the most you can lose is $50 a share, if it goes to zero.

Short a stock at $50 and there is no upper bound. At $100 you’ve lost $50 a share. At $200 you’ve lost $150. At $500 you’ve lost $450. The stock has no obligation to stop.

This asymmetry is the defining feature of short selling and the thing the exam wants you to be able to state. Maximum gain on a short is limited — the stock can only fall to zero, so you can only capture the full sale price. Maximum loss is unlimited.

Rule 201: the circuit breaker

Here’s what actually governs short sale pricing.

The trigger: a covered security’s price falls 10% or more below its previous day’s closing price.

What happens: short sales in that security may then only be executed at a price above the current national best bid.

How long: the remainder of the trading day, plus the entire following trading day.

Note what this means. On an ordinary day, in an ordinary stock, there’s no price restriction on short selling at all. The restriction is conditional, and the condition is a sharp decline.

The design intent is to let short selling function normally while preventing short sellers from piling onto a stock that’s already collapsing.

What it replaced: the original uptick rule, SEC Rule 10a-1, required short sales to be executed at a price above the last different price. It applied all the time, in every covered security. The SEC eliminated it in 2007 and adopted the Rule 201 alternative uptick approach in 2010.

If your study material describes short selling as requiring an uptick generally, it’s describing a rule that was removed before many SIE candidates started working.

Rule 203: the locate requirement

Before accepting or effecting a short sale, a broker-dealer must have one of three things:

1. Borrowed the security
2. Entered into a bona fide arrangement to borrow it
3. Reasonable grounds to believe the security can be borrowed and delivered by the settlement date

And the basis for that belief must be documented.

This is the locate requirement, and it’s the rule that addresses naked short selling — selling short without having borrowed or located the shares.

One exception: market makers engaged in bona fide market making are excepted from the locate requirement, because they need to be able to quote both sides continuously without a locate for every quote. “Bona fide” does real work in that sentence — the exception doesn’t cover a market maker using the designation as cover for directional short positions.

Rule 204: close-out, and what T+1 changed

If a short sale fails to deliver, the clearing participant must close out the fail by purchasing or borrowing securities of like kind and quantity.

The rule’s deadline is written relative to settlement: by no later than the beginning of regular trading hours on the settlement day following the settlement date.

That phrasing matters, because it means the deadline moves whenever the settlement cycle moves.

Settlement cycle	Short-sale close-out deadline
T+3 (pre-2017)	T+4
T+2 (2017–2024)	T+3
T+1 (since May 2024)	T+2

The SEC said so explicitly when it adopted T+1: shortening the cycle “reduces the time frames to effect the closeout of most types of fail-to-deliver positions under Rule 204.”

The rule text never changed. The practical deadline moved by a day, twice. Any source that states a fixed number without saying which settlement cycle it assumes is a source to check.

Fails from long sales and from bona fide market making get additional time under Rule 204. The SIE doesn’t test those variations in detail — that’s Series 7 and Series 57 territory — but knowing the short-sale deadline tracks settlement is worth carrying.

Threshold securities

When fails to deliver in a security become persistent, it gets flagged.

A threshold security is a registered equity security where, for five consecutive settlement days, the aggregate fails to deliver at a registered clearing agency total:

• 10,000 shares or more, and
• at least 0.5% of the issuer’s total shares outstanding

Both conditions, not either. The exchanges publish threshold security lists daily, and securities on the list carry mandatory close-out requirements.

Order marking

Rule 200 requires every sell order to be marked long, short, or short exempt.

A seller may mark an order “long” only if they actually own the security and either have it in their possession or reasonably expect to deliver it by settlement.

Mismarking is a genuine violation, not a clerical matter. Marking a short sale as long evades the locate requirement, the circuit breaker, and the close-out rules simultaneously.

Two adjacent restrictions

Rule 105 of Regulation M. If you sold a security short during the restricted period before a public offering is priced — generally the five business days before pricing — you may not purchase that security in the offering from an underwriter or broker-dealer participating in it. The rule stops traders from driving a price down before pricing and then covering with cheap offering shares. It’s enforced regularly.

Short against the box. Selling short a security you already own. Historically used to defer taxable gains; the constructive sale rules in the Taxpayer Relief Act of 1997 largely eliminated that benefit.

Why the exam cares

Short selling sits at the intersection of three areas the SIE tests separately: margin mechanics, prohibited activities, and market structure.

It’s also where the risk concepts become concrete. A short position carries unlimited loss potential, recall risk, borrow costs, and dividend liability — none of which apply to a long position. When a question asks about the risks of a strategy, a short position has a longer list than almost anything else on the exam.

Common misconceptions

“You can only sell short on an uptick.” That rule was eliminated in 2007. Rule 201 is a circuit breaker triggered by a 10% decline, after which shorts must execute above the national best bid.

“Rule 201 always applies.” Only after a security falls 10% or more from the prior close. Otherwise there’s no price restriction.

“You can short in a cash account.” No. Short sales require a margin account.

“Maintenance margin is 25% for everything.” 25% long, 30% short.

“Maximum loss on a short is the amount invested.” It’s unlimited. Maximum gain is limited, since the stock can only fall to zero.

“Naked shorting is always illegal.” The locate requirement has a bona fide market making exception. Abusive naked shorting is prohibited; the mechanism itself has a narrow legitimate use.

“The short seller keeps the dividends.” The short seller owes them to the lender.

“Close-out is T+3.” It was, under T+2 settlement. Under T+1 it’s T+2 — the rule is written relative to the settlement date.

“A threshold security is any stock with a lot of fails.” Both conditions must be met for five consecutive settlement days: 10,000 shares or more and at least 0.5% of shares outstanding.

What to do with this info

1. Replace the uptick rule in your head. The current mechanism is a 10% circuit breaker plus a bid test, in effect for that day and the next.
2. Memorise 25 long / 30 short. It’s a reliable exam point and easy to reverse under pressure.
3. State the risk asymmetry precisely. Unlimited loss, limited gain. Questions often ask for both halves.
4. Remember the three obligations of borrowing — dividends owed, recall risk, borrow cost. They’re what separates a short from a long beyond the direction.
5. Treat close-out timing as settlement-relative, not a fixed number. Same discipline as Reg T’s payment deadline.
6. Check any source describing short sale rules against the 2007 elimination of Rule 10a-1. Material that still teaches the tick test is dated, and probably dated elsewhere too.

Related resources

• Cash vs margin accounts — why a short sale can’t happen in a cash account
• Prohibited activities and trading violations — where mismarking and abusive shorting become enforcement matters
• T+1 settlement explained — the change that moved the close-out deadline
• Every number and formula on the SIE — margin requirements and settlement figures in one reference
• Systematic vs unsystematic risk — where unlimited-loss exposure sits in the risk framework
• Free SIE practice exam — a domain-scored diagnostic