# What Is Marginable? Reg T, Maintenance & Margin Calls

Published: 2026-04-19
Author: Warren Team
URL: https://www.heywarren.com/blog/marginable-securities-margin

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You log into your brokerage app, ready to deploy a margin loan against your favorite small-cap stock — and the platform refuses. Your "buying power" reads zero against that position, even though you have plenty of [equity](/blog/equity-meaning-in-business) elsewhere. What gives? The answer lies in a single regulatory concept most retail investors never learn until it bites them: marginability. So what is marginable, exactly, and why does the same broker treat your Apple shares as good collateral but your $4 biotech as worthless for borrowing?

A marginable security is one your broker — under [Federal Reserve](https://www.federalreserve.gov/), [FINRA](https://www.finra.org/), and exchange rules — will accept as collateral for a margin loan. Get this wrong and you can blow up your account during a margin call you never saw coming. Get it right and you understand exactly how much real leverage sits behind your portfolio, where the trip-wires are buried, and why your broker can change the rules mid-trade. This guide walks through the regulatory framework, what qualifies (and what doesn't), the math behind margin calls, the Pattern Day Trader rule, and the tax treatment of margin interest. By the end, you'll read your account's "marginable equity" line the way a compliance officer does.

## What Is Marginable? The Regulatory Definition

A marginable security is any financial instrument that satisfies Federal Reserve Regulation T, FINRA Rule 4210, and your broker's house requirements as eligible collateral for a margin loan. In practice, that means most [NYSE](https://www.nyse.com/)- and NASDAQ-listed stocks above $5, most ETFs, investment-grade bonds, and seasoned mutual funds. Non-marginable securities can still trade in your margin account — they just contribute zero to your buying power.

![Three stacked rule sets govern marginability — Federal Reserve Reg T sets the initial requirement, FINRA Rule 4210 sets the maintenance floor, and broker house requirements sit on top; the strictest always wins.](data:image/svg+xml,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20viewBox%3D%220%200%20875%20125%22%20width%3D%22875%22%20height%3D%22125%22%20role%3D%22img%22%3E%3Ctitle%3EFlow%20diagram%3C%2Ftitle%3E%3Crect%20width%3D%22100%25%22%20height%3D%22100%25%22%20fill%3D%22%23f8fafc%22%2F%3E%3Crect%20x%3D%2230%22%20y%3D%2225%22%20width%3D%22170%22%20height%3D%2275%22%20rx%3D%2210%22%20fill%3D%22white%22%20stroke%3D%22%232563eb%22%20stroke-width%3D%222%22%2F%3E%3Ctext%20x%3D%22115%22%20y%3D%2258.5%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3EFed%20%2F%20Reg%20T%3C%2Ftext%3E%3Ctext%20x%3D%22115%22%20y%3D%2278.5%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2211%22%20fill%3D%22%2364748b%22%3E50%25%20initial%20margin%3C%2Ftext%3E%3Cline%20x1%3D%22205%22%20y1%3D%2262.5%22%20x2%3D%22237%22%20y2%3D%2262.5%22%20stroke%3D%22%2364748b%22%20stroke-width%3D%222%22%2F%3E%3Cpolygon%20points%3D%22244%2C62.5%20235%2C57.5%20235%2C67.5%22%20fill%3D%22%2364748b%22%2F%3E%3Crect%20x%3D%22245%22%20y%3D%2225%22%20width%3D%22170%22%20height%3D%2275%22%20rx%3D%2210%22%20fill%3D%22white%22%20stroke%3D%22%232563eb%22%20stroke-width%3D%222%22%2F%3E%3Ctext%20x%3D%22330%22%20y%3D%2258.5%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3EFINRA%204210%3C%2Ftext%3E%3Ctext%20x%3D%22330%22%20y%3D%2278.5%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2211%22%20fill%3D%22%2364748b%22%3E25%25%20maintenance%20floor%3C%2Ftext%3E%3Cline%20x1%3D%22420%22%20y1%3D%2262.5%22%20x2%3D%22452%22%20y2%3D%2262.5%22%20stroke%3D%22%2364748b%22%20stroke-width%3D%222%22%2F%3E%3Cpolygon%20points%3D%22459%2C62.5%20450%2C57.5%20450%2C67.5%22%20fill%3D%22%2364748b%22%2F%3E%3Crect%20x%3D%22460%22%20y%3D%2225%22%20width%3D%22170%22%20height%3D%2275%22%20rx%3D%2210%22%20fill%3D%22white%22%20stroke%3D%22%232563eb%22%20stroke-width%3D%222%22%2F%3E%3Ctext%20x%3D%22545%22%20y%3D%2258.5%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3EHouse%20Rules%3C%2Ftext%3E%3Ctext%20x%3D%22545%22%20y%3D%2278.5%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2211%22%20fill%3D%22%2364748b%22%3E30%E2%80%93100%25%20broker%20minimum%3C%2Ftext%3E%3Cline%20x1%3D%22635%22%20y1%3D%2262.5%22%20x2%3D%22667%22%20y2%3D%2262.5%22%20stroke%3D%22%2364748b%22%20stroke-width%3D%222%22%2F%3E%3Cpolygon%20points%3D%22674%2C62.5%20665%2C57.5%20665%2C67.5%22%20fill%3D%22%2364748b%22%2F%3E%3Crect%20x%3D%22675%22%20y%3D%2225%22%20width%3D%22170%22%20height%3D%2275%22%20rx%3D%2210%22%20fill%3D%22white%22%20stroke%3D%22%232563eb%22%20stroke-width%3D%222%22%2F%3E%3Ctext%20x%3D%22760%22%20y%3D%2258.5%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3EStrictest%20Wins%3C%2Ftext%3E%3Ctext%20x%3D%22760%22%20y%3D%2278.5%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2211%22%20fill%3D%22%2364748b%22%3Eapplied%20to%20your%20account%3C%2Ftext%3E%3C%2Fsvg%3E)

*Three stacked rule sets govern marginability — Federal Reserve Reg T sets the initial requirement, FINRA Rule 4210 sets the maintenance floor, and broker house requirements sit on top; the strictest always wins.*

Three layers of rules stack on top of each other. The Federal Reserve Board sets initial margin through Regulation T. FINRA sets the floor for ongoing maintenance margin under Rule 4210. Your broker — Schwab, Fidelity, Robinhood, Interactive Brokers — adds "house requirements" on top, often higher than the regulatory minimum. The strictest rule wins. A stock that is technically marginable under Reg T might still get a 100% house requirement if your broker considers it too volatile or you hold a concentrated position.

### Reg T: The 50% Initial Margin Rule

Regulation T, enforced by the Federal Reserve since 1934, requires you to put up at least 50% of the purchase price for most equity trades on margin. That means $10,000 cash buys $20,000 of marginable stock — your broker lends you the other $10,000 against the position itself.

### FINRA Rule 4210: The 25% Maintenance Floor

After purchase, FINRA Rule 4210 requires you maintain at least 25% equity in your account at all times. Equity is the market value of your securities minus the margin loan. Drop below 25% and you trigger a margin call. Brokers commonly set house maintenance at 30-40% to give themselves a buffer.

![Margin requirement waterfall: cash to buying power to maintenance threshold](data:image/svg+xml;base64,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)

## What Qualifies as a Marginable Security?

Most listed [equities](/blog/what-is-equities) and bonds qualify. The Federal Reserve maintains a list of OTC equity issues approved for margin, but the simpler rule of thumb covers 95% of cases: if it trades on the NYSE or NASDAQ, costs more than $5, and isn't freshly issued, it's almost certainly marginable. Below are the standard categories every brokerage applies.

### The Marginable List

- **NYSE/NASDAQ stocks above $5** — the bread-and-butter category, typically 50% initial requirement
- **Most ETFs** — including broad-market index funds; some leveraged/inverse products require higher margin (often 90%)
- **Mutual funds** — marginable only after a 30-day holding period under Reg T
- **Investment-grade corporate bonds** — usually 30% initial requirement
- **U.S. Treasuries and government bonds** — as low as 1-10% requirement, the most loan-friendly collateral on the planet
- **Options writing** — covered calls and cash-secured puts can serve as collateral; bought (long) options never count

### The Non-Marginable List

- **Stocks under $5** per Reg T's price floor
- **IPOs in the first 30 days** of public trading
- **OTC Pink Sheets and Bulletin Board stocks** not on the Fed's approved OTC list
- **Most penny stocks** regardless of where they trade
- **Some leveraged/inverse ETFs** (broker-specific)
- **Recently issued bonds** during their distribution period
- **Concentrated single-stock positions** at broker discretion

![Marginable versus non-marginable securities by asset class](data:image/svg+xml;base64,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)

## How Margin Math Actually Works: A $10K Worked Example

The mechanics matter more than the rules because they determine when your broker liquidates you. Suppose you deposit $10,000 cash and buy $20,000 of a marginable stock at the 50% Reg T initial requirement. Your broker lends you $10,000. Equity equals $10K, the loan equals $10K, position value equals $20K. Now run the price down and watch the equity ratio collapse.

![A broker using a 30% house maintenance requirement calls margin at $14,286 position value — $953 earlier than the FINRA 25% floor of $13,333 — on a $10,000 loan.](data:image/svg+xml,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20viewBox%3D%220%200%20800%20210%22%20width%3D%22800%22%20height%3D%22210%22%20role%3D%22img%22%3E%3Ctitle%3EComparison%3C%2Ftitle%3E%3Crect%20width%3D%22100%25%22%20height%3D%22100%25%22%20fill%3D%22%23f8fafc%22%2F%3E%3Ctext%20x%3D%22230%22%20y%3D%2257.5%22%20text-anchor%3D%22end%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3EFINRA%2025%25%20floor%3C%2Ftext%3E%3Crect%20x%3D%22240%22%20y%3D%2225%22%20width%3D%22419.98110037799245%22%20height%3D%2255%22%20rx%3D%226%22%20fill%3D%22%232563eb%22%2F%3E%3Ctext%20x%3D%22671.9811003779924%22%20y%3D%2257.5%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22700%22%20fill%3D%22%232563eb%22%3E%2413K%3C%2Ftext%3E%3Ctext%20x%3D%22230%22%20y%3D%22152.5%22%20text-anchor%3D%22end%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3EHouse%2030%25%20floor%3C%2Ftext%3E%3Crect%20x%3D%22240%22%20y%3D%22120%22%20width%3D%22450%22%20height%3D%2255%22%20rx%3D%226%22%20fill%3D%22%237c3aed%22%2F%3E%3Ctext%20x%3D%22702%22%20y%3D%22152.5%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22700%22%20fill%3D%22%237c3aed%22%3E%2414K%3C%2Ftext%3E%3C%2Fsvg%3E)

*A broker using a 30% house maintenance requirement calls margin at $14,286 position value — $953 earlier than the FINRA 25% floor of $13,333 — on a $10,000 loan.*

If the stock drops 33%, your $20K position falls to $13,333. The loan still sits at $10,000 (debt doesn't move). Equity is now $13,333 minus $10,000 equals $3,333. The equity ratio — equity divided by position value — equals $3,333 / $13,333 = 25%. You've hit FINRA's maintenance floor exactly. The next tick down triggers a margin call.

To compute your margin call price for a 25% maintenance requirement, the formula is: **call price = loan / (1 − maintenance %) / shares**. Brokers using a 30% house maintenance call earlier — at roughly $14,286 instead of $13,333. That gap is why house requirements matter more than the FINRA minimum in real-world trading.

### The Margin Call Itself

Once equity drops below the maintenance floor, the broker issues a Reg T call (for new purchases) or a maintenance call. You typically have **two to five business days** to either deposit cash, deposit additional marginable securities, or sell positions to restore equity. Miss the deadline and the broker liquidates positions of its choosing — without your input, often at the worst possible price.

![Margin call mechanics flow from breach to liquidation](data:image/svg+xml;base64,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)

## House Requirements: Why Your Broker Can Move the Goalposts

House requirements are broker-imposed margin rules above the regulatory minimum, and they can change overnight. During the January 2021 GameStop episode, multiple brokers raised the maintenance requirement on GME and other "meme stocks" to 100% — meaning no margin allowed at all. Traders holding the stock on margin saw their buying power vanish and faced sudden margin calls through no fault of their own.

![Once equity breaches the maintenance floor, borrowers have a narrow window to cure before the broker liquidates positions without notice or client input.](data:image/svg+xml,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20viewBox%3D%220%200%20800%20149%22%20width%3D%22800%22%20height%3D%22149%22%20role%3D%22img%22%3E%3Ctitle%3ETimeline%3C%2Ftitle%3E%3Crect%20width%3D%22100%25%22%20height%3D%22100%25%22%20fill%3D%22%23f8fafc%22%2F%3E%3Cline%20x1%3D%22137.5%22%20y1%3D%2255%22%20x2%3D%22662.5%22%20y2%3D%2255%22%20stroke%3D%22%23cbd5e1%22%20stroke-width%3D%223%22%2F%3E%3Ccircle%20cx%3D%22137.5%22%20cy%3D%2255%22%20r%3D%2224%22%20fill%3D%22white%22%20stroke%3D%22%23cbd5e1%22%20stroke-width%3D%222%22%2F%3E%3Ctext%20x%3D%22137.5%22%20y%3D%2260%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2215%22%20font-weight%3D%22700%22%20fill%3D%22%230f172a%22%3E1%3C%2Ftext%3E%3Ctext%20x%3D%22137.5%22%20y%3D%22101%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2212%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3EEquity%20breach%3C%2Ftext%3E%3Ctext%20x%3D%22137.5%22%20y%3D%22119%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2210%22%20fill%3D%22%2364748b%22%3Edrops%20below%20maintenance%20%25%3C%2Ftext%3E%3Ccircle%20cx%3D%22312.5%22%20cy%3D%2255%22%20r%3D%2224%22%20fill%3D%22white%22%20stroke%3D%22%23cbd5e1%22%20stroke-width%3D%222%22%2F%3E%3Ctext%20x%3D%22312.5%22%20y%3D%2260%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2215%22%20font-weight%3D%22700%22%20fill%3D%22%230f172a%22%3E2%3C%2Ftext%3E%3Ctext%20x%3D%22312.5%22%20y%3D%22101%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2212%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3ECall%20issued%3C%2Ftext%3E%3Ctext%20x%3D%22312.5%22%20y%3D%22119%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2210%22%20fill%3D%22%2364748b%22%3Ebroker%20notifies%20account%3C%2Ftext%3E%3Ccircle%20cx%3D%22487.5%22%20cy%3D%2255%22%20r%3D%2224%22%20fill%3D%22%232563eb%22%20stroke%3D%22%232563eb%22%20stroke-width%3D%223%22%2F%3E%3Ctext%20x%3D%22487.5%22%20y%3D%2260%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2215%22%20font-weight%3D%22700%22%20fill%3D%22white%22%3E3%3C%2Ftext%3E%3Ctext%20x%3D%22487.5%22%20y%3D%22101%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2212%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3ECure%20window%3C%2Ftext%3E%3Ctext%20x%3D%22487.5%22%20y%3D%22119%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2210%22%20fill%3D%22%2364748b%22%3E2%E2%80%935%20business%20days%3C%2Ftext%3E%3Ccircle%20cx%3D%22662.5%22%20cy%3D%2255%22%20r%3D%2224%22%20fill%3D%22white%22%20stroke%3D%22%23cbd5e1%22%20stroke-width%3D%222%22%2F%3E%3Ctext%20x%3D%22662.5%22%20y%3D%2260%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2215%22%20font-weight%3D%22700%22%20fill%3D%22%230f172a%22%3E4%3C%2Ftext%3E%3Ctext%20x%3D%22662.5%22%20y%3D%22101%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2212%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3EForced%20sale%3C%2Ftext%3E%3Ctext%20x%3D%22662.5%22%20y%3D%22119%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2210%22%20fill%3D%22%2364748b%22%3Ebroker%20chooses%20positions%3C%2Ftext%3E%3C%2Fsvg%3E)

*Once equity breaches the maintenance floor, borrowers have a narrow window to cure before the broker liquidates positions without notice or client input.*

Brokers typically apply higher house requirements in three scenarios. First, **volatility**: stocks with implied volatility above some threshold (often 100%) get bumped to 75% or 100% maintenance. Second, **concentration**: if a single position exceeds 25-50% of your portfolio, the marginal shares get a higher requirement. Third, **idiosyncratic risk**: pending mergers, going-concern warnings, or short-squeeze candidates often trigger restrictions. The lesson is brutal but simple — marginable status is a moving target, not a fixed property of the security.

## Day Trading and the Pattern Day Trader Rule

If you execute four or more day trades within five business days, FINRA designates you a **Pattern Day Trader** (PDT) and your account must maintain at least $25,000 in equity. The trade-off is meaningful: PDT accounts get **4x intraday buying power** instead of the standard 2x — but only on marginable securities, and only intraday.

Hold a position overnight and buying power reverts to the 2x Reg T overnight limit. Drop below $25K equity and your account gets restricted to cash trades only for 90 days. Many retail accounts get accidentally trapped here — the four-trade rule includes round trips, so two opens and two closes count as four day trades, not two.

## Tax Treatment: The Margin Interest Deduction

Margin interest is potentially deductible — but only as an **investment interest expense** against net investment income, and only if you itemize. You report it on **Form 4952**, and the deduction is capped at your investment income (interest, non-qualified dividends, short-term capital gains). Excess interest carries forward indefinitely.

Qualified dividends and long-term capital gains don't count as investment income unless you elect to treat them as ordinary — which sacrifices the preferential tax rate. For most retail investors taking the standard deduction, the margin-interest tax shield is illusory. Run the numbers before you assume the [IRS](https://www.irs.gov/) is subsidizing your leverage.

## Common Mistakes and Famous Margin Disasters

The first mistake is treating marginability as permanent. A stock that's 50% margin today can flip to 100% tomorrow if your broker reclassifies it. The second is ignoring concentration discounts — a $500K position in one stock often gets a higher house requirement than five $100K positions across sectors. The third is the **meme-stock trap**: holding a high-flying name into earnings or a corporate event when brokers preemptively raise margin.

The historical lesson is older. In the 1929 crash, retail investors borrowed up to 90% against stocks with no maintenance requirement at all. When prices fell, cascading margin calls forced selling that drove prices lower, triggering more calls — a feedback loop that wiped out a generation of wealth. Reg T was passed in 1934 specifically to prevent a repeat. Modern margin disasters — Long-Term Capital Management in 1998, Archegos in 2021, the GameStop squeeze — all share the same DNA: leverage against positions whose marginable status changed faster than the borrower could react.

## Conclusion

Understanding what is marginable is the difference between using leverage as a tool and getting used by it. Five takeaways to internalize: (1) marginability is governed by Reg T, FINRA Rule 4210, and house requirements stacked together — the strictest wins. (2) The standard formula is 50% initial margin, 25% maintenance, but brokers routinely set higher floors. (3) Stocks under $5, recent IPOs, OTC pink sheets, and bought options never count as collateral. (4) Margin calls give you 2-5 days to cure before forced [liquidation](/blog/define-liquidation) — at prices you don't control. (5) Margin interest is deductible only against net investment income on Form 4952, and only if you itemize.

The margin landscape will keep tightening as regulators digest each new volatility episode. Expect more dynamic house requirements, faster reclassifications during squeeze events, and tighter concentration rules. The investors who navigate this best will be those who treat marginability as a live variable to monitor — not a static spec sheet.

Ready to put this knowledge to work? Try Warren, your AI financial advisor — get personalized, conflict-free guidance at heywarren.com

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## Related Reading

**More from Warren**:

- [Copayments vs. Coinsurance: Key Differences Explained](/blog/copayments-vs-coinsurance)
- [What Renting and Owning a House Really Cost](/blog/renting-and-owning-a-house)
- [What Is a Liability?](/blog/examples-liabilities)
**Authoritative sources**:
- [SEC Investor.gov — Investing Basics](https://www.investor.gov/introduction-investing/investing-basics)
- [FINRA — Investor Education](https://www.finra.org/investors)