Cash vs margin accounts: differences, rules and which fits you

When you open a brokerage account in the US, one of the first questions on the form is whether you want a cash account or a margin account. It looks like an administrative checkbox. It is actually a choice about whether your broker may lend you money, and that one decision changes what you can trade, how fast you can reuse cash, and how much you can lose.

In a cash account you pay for everything you buy, in full, with your own money. In a margin account the broker can lend you part of the purchase price, using your investments as collateral. Borrowing opens doors (short selling, some options strategies, more flexibility with unsettled cash) and adds costs and risks that a cash account simply does not have.

This guide walks through how each account works, the US rules that govern them as of 2026, a worked example of the same purchase made both ways, and the questions to ask before choosing. It explains the mechanics only; it does not recommend either type.

What a cash account is

A cash account is the default, simplest kind of brokerage account. Every purchase must be paid in full. You deposit money, you buy securities with that money, and when you sell, the proceeds come back as cash once the trade settles.

The rules come from the Federal Reserve's Regulation T, which governs how brokers extend credit. Its cash-account section (12 CFR 220.8) lets a broker buy a security for you only if you already have the funds in the account, or the broker accepts in good faith that you will pay promptly. Since May 28, 2024, most US stock, ETF and bond trades settle one business day after the trade (T+1); a Monday sale settles Tuesday.

Because there is no loan, a cash account has no interest charges and no margin calls. If a stock you own falls 40%, your account is worth 40% less on that position, but nobody asks you to deposit more money and nothing is sold against your will.

The cost of that simplicity is a constraint on reusing money. Proceeds from a sale are not settled until T+1. If you buy something with unsettled proceeds and then sell it again before those proceeds settle, you can trigger a good-faith violation, and selling a stock you never paid for at all is free-riding, which brings a 90-day freeze. The rules behind those labels are covered in Cash account violations: good faith, free-riding and liquidation.

What a margin account is

A margin account adds a line of credit secured by the securities in it. When you buy a marginable stock, you pay part of the price and the broker lends the rest. The loan is called your debit balance, and the broker charges interest on it, usually at a variable rate that falls as the balance grows.

Opening one requires a margin agreement. By signing it you pledge the securities in the account as collateral and accept the firm's rules on how much you may borrow, when it may demand more money, and its right to sell your holdings if you fall short. FINRA requires firms to hand customers a margin disclosure statement that spells out these risks. Most margin agreements also allow the firm to lend out the securities you bought on margin, which is how other customers are able to sell them short.

Three numbers define the borrowing limits in the US as of 2026:

• $2,000 minimum equity. Under FINRA Rule 4210 you need at least $2,000 of equity (or 100% of the purchase price, if less) to trade on margin. Below it you can still trade in the account, but only with available cash.
• 50% initial margin. Regulation T (12 CFR 220.12) limits the loan on a stock purchase to 50% of its value. To buy $10,000 of stock you must put up at least $5,000.
• 25% maintenance margin. After the purchase, FINRA requires your equity to stay at or above 25% of the market value of the margin stock. Firms can, and often do, set a higher house requirement, such as 30% or 40%, and higher still for volatile stocks.

When equity falls below the maintenance level, you get a margin call: deposit cash or securities, or the firm may sell your holdings, without notice and in the order it chooses. The arithmetic of when that happens is worked out in Margin calls: when they trigger, how to calculate them, what to do, and the full mechanics of borrowing to buy are in Buying on margin: how margin loans, interest and leverage work.

The same purchase, made both ways

That doubling, in both directions, is the essence of the margin trade-off. A margin account does not make a stock better or worse; it makes the result of owning it larger.

Other things a margin account allows

Borrowing is not the only reason people open margin accounts. Several activities need one even if you never take a loan on a stock purchase:

• Short selling. Selling borrowed shares, in the hope of buying them back cheaper, is only possible in a margin account, because the short position is effectively a loan of stock.
• Many options strategies. Writing uncovered options and most multi-leg spreads need margin. Buying calls or puts, writing covered calls and writing cash-secured puts are often allowed in a cash account, depending on the firm's options approval levels (see Options basics: how calls and puts work, with payoff diagrams).
• Using unsettled proceeds. In a margin account the broker can extend credit across the one-day settlement gap, so buying and selling with unsettled funds does not cause cash-account violations.
• Borrowing against holdings. Some investors withdraw cash against their portfolio instead of selling, which avoids realizing a taxable gain but adds a loan that can be called if prices fall.

Margin accounts also bring the day-trading rules into play. Until 2026 that meant the pattern-day-trader test and its $25,000 minimum; FINRA has since replaced it with an intraday margin standard, with a phase-in that runs to October 2027. See Pattern day trader rule: the legacy PDT test and the 2026 replacement.

Side-by-side comparison

Choosing between them

There is no universally right answer, but a few questions sort most people out.

Do you need anything only margin offers? If you plan to buy and hold stocks and funds, a cash account does everything you need. If you plan to sell short or write spreads, you will need margin.

How would you react to a margin call? A margin call arrives when prices are already falling, often quickly. If you would not have spare cash to deposit, the likely outcome is a forced sale at a low price. Many people open a margin account for flexibility but never borrow; that is possible, but the account still allows borrowing, so it takes discipline.

Is it a retirement account? IRAs and similar accounts generally cannot borrow, because pledging retirement assets as collateral has tax consequences. Some firms offer a "limited margin" IRA that only removes settlement waits, without any loan (not independently verified as of October 2026; check your firm's terms).

Can you switch later? Usually yes: most firms let you add or remove margin privileges on an existing account, subject to approval. Removing margin requires paying off any debit balance first.

Common misunderstandings

• "Margin is free money." It is a loan with interest, secured by your holdings, and the lender can sell them without asking.
• "A margin account means I'm borrowing." Only if you buy more than your cash covers or withdraw against holdings. Holding a margin account with no debit balance costs nothing.
• "SIPC protects me from losses." SIPC covers missing assets if a member broker fails, up to $500,000 including $250,000 of cash. It never covers a fall in market value, in either account type.
• "Cash accounts have no rules." They have settlement rules, and breaking them can restrict the account for 90 days.

How Finabase helps

Finabase is a research and tracking app; it does not open brokerage accounts, lend money or apply margin. Whichever account you use at your broker, you can mirror your positions in a Finabase portfolio, which records each buy and sell with its date and shows average cost, unrealized and realized gains at live prices. Before a purchase, a symbol page shows the quote, profile and financials, and the screener filters stocks by price, sector and other fields, useful for spotting the high-volatility names that firms often put under higher house margin requirements.

Frequently asked questions

Is a cash account safer than a margin account?

In one specific sense, yes: in a cash account you cannot lose more than you invested and nothing is sold to repay a loan. Both accounts carry the same market risk on the securities themselves and the same SIPC protection against broker failure.

How much money do I need for a margin account?

FINRA Rule 4210 requires at least $2,000 of equity to trade on margin, and firms may require more. Below $2,000 you can still trade in the account, but only with available cash.

Can I day trade in a cash account?

Yes, as long as each purchase is made with settled funds. Day-trading margin rules do not apply to cash accounts, but reusing unsettled sale proceeds too quickly can trigger a good-faith violation, and repeated violations can restrict the account.

Do I pay interest just for having a margin account?

No. Interest is charged only on money you actually borrow, the debit balance. A margin account with no loan outstanding accrues no margin interest.

Can a margin account lose more than I deposited?

Yes. If prices fall far enough and fast enough, the securities may be sold for less than the loan, leaving a debit balance that you still owe the broker.

Summary

A cash account buys only with money you have, settles trades T+1, and cannot lose more than you put in; its main limits are no short selling and waiting for settlement before reusing proceeds. A margin account adds a secured loan: up to 50% of a stock purchase under Regulation T, a $2,000 minimum equity and a 25% FINRA maintenance floor (often higher at the firm), with interest and margin calls attached. It unlocks short selling, more options strategies and settlement flexibility, and it magnifies both gains and losses. The right choice depends on what you plan to trade and on whether you could meet a margin call when prices are falling.