Reg SHO Threshold List: What It Is and Why It Matters

Direct answer: The Reg SHO threshold list is a daily roster published by US exchanges (NYSE, Nasdaq) identifying securities that accumulate too many fails-to-deliver—settlement failures after a transaction. A stock appears when these failures exceed 0.5% of shares outstanding or 10,000 shares for five consecutive trading days. Inclusion triggers accelerated close-out obligations for brokers.

Regulation SHO: The Framework

Regulation SHO is an SEC rule adopted in January 2005 to govern short selling and curb abusive practices tied to delivery failures. Before 2005, some players maintained short positions without ever delivering the sold shares. "Naked shorts" persisted, sometimes for weeks.

Reg SHO imposes two mechanisms:

1. Locate requirement: before executing a short sale, a broker must locate shares to borrow. They must have reasonable grounds to believe they can borrow and deliver the securities by settlement.
2. Close-out requirement: if a delivery failure persists, the broker must close the position within an imposed deadline—by buying back shares in the market or borrowing them.

The threshold securities list is one of Reg SHO's surveillance tools. It identifies securities where failures accumulate beyond a critical threshold.

The Threshold Securities List: Definition and Criteria

The threshold list tracks securities showing elevated aggregate fails-to-deliver over consecutive days. A fail-to-deliver occurs when a seller (or their broker) cannot deliver sold securities by the expected settlement date—typically T+2 for common stock.

Listing Criteria

A security joins the threshold securities list if both conditions hold for five consecutive trading days:

• Aggregate fails-to-deliver at the National Securities Clearing Corporation (NSCC) exceed 10,000 shares, AND
• The failure level represents at least 0.5% of total shares outstanding.

Once these criteria are met, the security appears on the list published by the exchange the following trading day. It remains while failures persist above the threshold. As soon as they drop below for one day, the stock exits.

Publication and Updates

Each US exchange (NYSE, Nasdaq, NYSE American) publishes its own threshold list daily on its official site, at end of day. Lists are dated for the trading day they apply to. Update cadence: every day the market is open.

Fails-to-Deliver: Where the Data Comes From

Fails-to-deliver are tallied by the National Securities Clearing Corporation (NSCC), the clearinghouse that settles the majority of US equity transactions. Each evening, the NSCC aggregates the day's failures and transmits this data to the SEC.

The SEC publishes twice monthly a summary file of aggregated fails-to-deliver, available at sec.gov/data in the "Fails-to-Deliver Data" section. These files cover the first half of the month (published around the 15th) and the second half (published early the following month). Each row shows, for a given security and settlement date, the total shares failing delivery that day.

Important: these SEC files show failures on a given date, not five-day cumulative totals. The threshold calculation (five consecutive days above 0.5% or 10,000 shares) is performed upstream by the exchanges, which publish the resulting list.

Consequences for a Threshold Security

Accelerated Close-Out Obligation

When a security appears on the threshold list, any broker holding an open short position (or having sold short) with a delivery failure must close that failure within a strict deadline:

• T+13 trading days from the original settlement date (T), the broker must buy back shares in the market ("buy-in") or borrow the securities to complete delivery.
• While the stock remains threshold, any new short sale faces enhanced locate requirements: the broker must pre-borrow shares before even accepting the client's short order ("pre-borrow").

Potential Price Impact

The obligation to close out within a tight window can create mechanical buying pressure. Brokers in failure must buy back in the market, sometimes when borrow supply is scarce. On a small-cap with tight float, this can amplify upside volatility if multiple players close simultaneously.

Conversely, threshold listing also signals the stock faces structural tension between short sellers and borrow availability. It's an indicator of friction, not necessarily direction.

Why Small-Caps Are Overrepresented

The 0.5% of shares outstanding threshold makes small-caps with tight floats mechanically more sensitive. Examples:

Shares outstanding	0.5% (threshold level)	Effective threshold applied
5 million	25,000 shares	25,000
2 million	10,000 shares	10,000
1 million	5,000 shares	10,000 (floor)
500 million	2.5 million	2.5 million

For a micro-cap with 2 million shares outstanding, 10,000 shares in failure for five days triggers inclusion. For a large-cap with 500 million shares, it takes 2.5 million failures—a very different order of magnitude.

Result: threshold lists contain a heavy proportion of small-caps, OTC stocks, and securities with reduced or illiquid float. That's where failures accumulate faster as a percentage of the float.

Where to Check the Threshold List in Practice

Official sources:

• Nasdaq Regulation SHO Threshold List: published daily at nasdaq.com (search "Reg SHO threshold securities").
• NYSE Regulation SHO Threshold List: published at nyse.com, Regulation section.
• SEC Fails-to-Deliver Files: available at sec.gov/data, "CNS Fails Data" file published twice monthly. These files show raw failures day by day, ticker by ticker.

These lists are dated and updated every trading day. A stock can enter and exit multiple times over a month, depending on whether failures persist or resolve.

Threshold List and Float: The FloatVerify Angle

FloatVerify displays the sourced and dated float for every US small-cap, noting the source of each figure (DEF 14A, 10-K, 10-Q, SC 13D, Section 16) and the filing date. When multiple sources diverge—for instance, float calculated from a 10-Q versus free float estimated by a platform—FloatVerify shows both figures in amber ("source split"), instead of arbitrarily choosing one.

The threshold list connection: the 0.5% of shares outstanding threshold directly depends on the denominator. If the real float is smaller than the official shares outstanding figure (frequent when a portion is locked by insiders), the pressure on borrow is even stronger than the threshold ratio suggests. FloatVerify shows that nuance—and flags when sources don't agree.

Recap

Point	Takeaway
Definition	List of securities with fails-to-deliver ≥ 0.5% of float or 10,000 shares for 5 consecutive trading days
Publication	Daily, by each exchange (NYSE, Nasdaq), end of trading day
Key consequence	Mandatory close-out of failures within T+13 days; enhanced locate requirement for new shorts
Data origin	NSCC (clearing), published in detail twice monthly by the SEC (sec.gov/data)
Small-cap sensitivity	The 0.5% threshold makes stocks with tight float mechanically more exposed to listing
FloatVerify reading	Float sourced, dated, divergences displayed (source split)—threshold ratio denominator visible and verified

FAQ

What is Regulation SHO?

Regulation SHO is an SEC rule adopted in 2005 to govern short selling and reduce fails-to-deliver. It requires brokers to locate shares before shorting and mandates rapid close-out when failures persist.

How does a stock end up on the threshold list?

A stock joins the threshold securities list when aggregate fails-to-deliver exceed 0.5% of shares outstanding or 10,000 shares for five consecutive trading days. Each exchange (NYSE, Nasdaq) publishes its own list daily.

Where can I check the Reg SHO threshold list?

Threshold lists are published daily by each exchange on their official sites. Find them at nasdaq.com, nyse.com, and the SEC aggregates fails-to-deliver data in CNS Fails files at sec.gov/data. Lists update every trading day.

What happens when a stock is on the threshold list?

A broker holding an open short position on a threshold security must close out delivery failures within a strict deadline: T+13 trading days from the original settlement date. While the stock remains listed, any new short sale faces enhanced locate requirements.

Reg SHO threshold list and float: what's the connection?

The 0.5% of shares outstanding threshold makes small-caps with tight floats more sensitive: 10,000 shares often triggers inclusion, where a large-cap would need millions of failures. A low-float stock appearing on the list signals structural tension between supply and demand for borrow.

Sources

• SEC Regulation SHO: sec.gov/rules/final/34-50103.htm — full text of the rule adopted in 2005
• SEC Fails-to-Deliver Data: sec.gov/data — CNS Fails files published twice monthly, detailing delivery failures by ticker and date
• Nasdaq Regulation SHO Threshold List: nasdaq.com — daily list of threshold securities on Nasdaq
• NYSE Regulation SHO: nyse.com — daily list and rule documentation
• FINRA Regulation SHO: finra.org — guides and FAQs on Reg SHO implementation by member brokers

See the float, sourced and dated, on FloatVerify.

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FloatVerify shows the float, dilution and cash burn of US small-caps, every number sourced and dated—and surfaces divergences between sources ("source split") instead of one falsely certain figure.

Disclaimer: FloatVerify is a data tool, not an investment advisory service. Nothing here is a recommendation to buy or sell. Data, not advice.