What it means
Short selling is legal and useful; abusive naked shorting is neither. Regulation SHO, adopted by the SEC in 2004, is the rulebook that draws the line between them.
A normal short sale borrows shares before selling them. A naked short sells without borrowing, creating phantom supply, and Reg SHO's architecture exists to make that hard and temporary.
The regulation's full text lives in 17 CFR Part 242, which sets out the locate requirement, the order-marking rules, and the close-out regime for failures to deliver. The locate requirement is the front door: before executing a short, the broker must have borrowed the shares, arranged to borrow them, or have reasonable grounds to believe they can be borrowed by settlement.
The close-out rule is the backstop: when failures to deliver persist in a stock beyond threshold levels, the broker must purchase shares to close the failure, and further shorting requires pre-borrowing. The threshold list, published by exchanges, names the stocks with heavy persistent failures, making the settlement plumbing visible to anyone who cares to look.
The rules carry real teeth: the SEC has brought enforcement actions against firms whose locate practices were fiction, and the 2008 crisis added temporary emergency orders tightening short sales in financials. For a non-finance reader, Reg SHO is the rule that a short seller must actually borrow the lawn mower before renting it out, and must return it when the system says the loan is overdue.
Order marking sounds clerical and is not. Every sell order must be marked long, short, or short exempt, and mismarking has produced some of the largest fines in the rule's history, because the tape is the regulator's raw evidence.
The rule interacts with the uptick debate's history: the original price-test restrictions were removed in 2007, and the crisis-era alternative uptick rule returned a circuit breaker that triggers only after a stock falls sharply. Options market makers sit in a special position: their hedging shorts keep derivative markets liquid, which is why the exemptions exist and why policing their edges is a permanent supervision theme.
Outside the United States, parallel regimes took their own shape: the European Union requires disclosure of significant net short positions, trading the American plumbing approach for a transparency one.
In practice
Real-world examples.
Example
A broker documents a locate before executing a customer's short sale in a hard-to-borrow stock. The borrow desk signed before the order went in. If a regulator later asks, the dated record proves the shares were available to borrow.
Example
A stock lands on the threshold list after persistent failures to deliver, triggering mandatory close-outs. Any new short sale in the stock now requires shares to be pre-borrowed. The list is published, so anyone can see which names carry heavy settlement friction.
Example
The SEC fines a firm whose locate records showed shares borrowed from sources that never held them. The locate was a paper exercise rather than a real check. The case shows why regulators read the records behind the rule as closely as the rule itself.
Formula
Calculation
The mechanics: locate before shorting (borrowed, arranged, or reasonable grounds), mark sell orders long or short, and close out threshold-list failures to deliver after the regulatory window, with pre-borrow required for new shorts in threshold securities.
Worked example. A security generally joins the threshold list when, for five consecutive settlement days, aggregate failures to deliver total at least 10,000 shares and at least 0.5% of shares outstanding. For a fictional company with 20,000,000 shares outstanding, 0.5% is 20,000,000 x 0.005 = 100,000 shares. Failures of 120,000 shares on each of five consecutive days clear both tests, whereas failures of 60,000 shares clear the 10,000-share test but not the 0.5% test. Participants must then close out failures that have persisted for 13 consecutive settlement days by purchasing shares of like kind and quantity.Case study
Seen in the real world.
This case study is fictional and illustrative. A made-up small-cap medical company lands on the threshold securities list after its failure-to-deliver numbers persist for weeks. Online forums claim a naked short conspiracy; the company's new investor relations chief asks its counsel what the rules actually say. The answer is a tour of Reg SHO: every short sale in its stock now requires a locate, persistent fails force close-out purchases, and new shorts need pre-borrowed shares, so the rules are already tighter for threshold names.
Counsel also punctures the mythology: most fails come from operational friction and market-maker exemptions, not a single villain, though enforcement actions show real violations do get prosecuted. Months later, settlement data normalises as borrowing loosens, and the stock leaves the list. The IR chief's summary to the board becomes the company's standing guidance: the threshold list is a plumbing report, not a verdict, and the correct response is transparent disclosure and clean operations, because the regulatory machinery watches settlement failures far more reliably than it watches anyone's narrative.
Watch out
Common mistakes.
- Assuming all short selling is naked; legal shorts borrow first, and Reg SHO's locate rule is the paper trail that proves it.
- Reading the threshold list as proof of manipulation; most fails are operational, and the list measures settlement friction, not intent.
- Forgetting market-maker exemptions; bona fide market making gets modified close-out treatment, which is why fails can persist legally for a time.
Questions
People also ask.
What is Regulation SHO?
The SEC's 2004 short-sale framework in 17 CFR Part 242, requiring locates before shorting, accurate order marking, and close-out of persistent failures to deliver.
What is the locate requirement?
Before shorting, a broker must have borrowed the shares, arranged the borrow, or have reasonable grounds to believe the shares can be borrowed in time for settlement.
What happens to threshold stocks?
Persistent failures trigger mandatory close-out purchases, and further short sales require actual pre-borrowing rather than a locate.
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