Cash vs margin accounts

When you open a brokerage account, the first real decision is whether it is a cash account or a margin account. The app will nudge you toward margin because it is more profitable for the broker and "unlocks features". Here is what each actually means, in US terms first, with notes on how it differs elsewhere.

Cash account

You can only buy with money you have. No borrowing, no shorting stock, limited options strategies (usually just buying calls and puts, and covered calls).

The catch is settlement. When you sell a US stock, the proceeds settle the next business day (T+1). Options settle T+1 too. In a cash account, you are supposed to wait for settlement before spending that money on something you will sell before it settles. If you buy with unsettled funds and then sell before they settle, that is a good-faith violation. Three of those in a year and the broker restricts your account to settled funds only for 90 days.

In practice this means: with a $5,000 cash account, if you buy and sell $5,000 of stock on Monday, that cash is not fully usable again until Tuesday. You can effectively turn your whole account over once per day. For a swing trader holding days to weeks, this is invisible. For a day trader, it is a hard speed limit.

Margin account

The broker lends you money against the value of your holdings. In the US, Regulation T lets you borrow up to 50% of a stock purchase, so $10,000 of cash can buy $20,000 of stock. Intraday, brokers extend more (up to 4:1 for qualifying day traders, see the next lesson).

Margin also lets you:

Short sell stock (borrow shares, sell them, buy back later).
Trade more options strategies (spreads, naked puts at higher approval levels).
Ignore settlement for the most part, because the broker fronts the cash.
Trade futures, which require a margin account by definition.

What it costs:

Interest on borrowed money, charged daily, typically 6 to 13% per year at retail brokers and much less at a few competitive ones. Borrowing $10,000 at 10% costs about $2.74 a day, every day, whether the position moves or not.
Maintenance requirements. If your equity falls below a threshold (25% of position value by regulation, often 30 to 40% in practice), you get a margin call: deposit more or the broker sells your positions, at whatever price is available, without asking which ones.
Your shares can be lent out to short sellers, and some brokers keep the fee.

The arithmetic of leverage

Suppose you have $10,000 and buy $20,000 of stock on margin.

Stock move	Position value	Loan	Your equity	Your return
+10%	$22,000	$10,000	$12,000	+20%
0%	$20,000	$10,000	$10,000	0% (minus interest)
-10%	$18,000	$10,000	$8,000	-20%
-25%	$15,000	$10,000	$5,000	-50%
-50%	$10,000	$10,000	$0	-100%

Leverage doubles every outcome. A stock that halves, which happens to individual companies every year, takes your whole account. Somewhere before that, around the -25% to -35% mark depending on the broker's maintenance level, you would have been margin-called and sold out anyway, locking in the loss at the worst moment.

Key idea: A margin account is a loan with your portfolio as collateral, and the lender can seize the collateral when it is falling. Leverage multiplies gains and losses symmetrically, but the margin call makes the downside path-dependent: you can be right eventually and still be forced out.

Which should a beginner use?

A cash account, almost always, for the first several months. Reasons:

You cannot lose more than you deposited. With margin, a gap down on a leveraged position can leave you owing the broker.
Settlement acts as a natural brake on overtrading, which is the main beginner disease.
You are not paying interest on a strategy you have not proven.
Nothing you need to learn requires margin. Order types, position sizing, journaling and discipline all work in a cash account.

The reasonable exceptions: you specifically want to learn futures (margin by definition, but use micros), or you want to trade defined-risk option spreads, which need a margin account at most brokers even though the risk is capped.

If you do open a margin account, you can still trade it like a cash account by never buying more than your cash balance. The danger is not the account type; it is the button that lets you exceed it at 2 pm on a day you are sure.

Outside the US

UK and EU: stock margin lending is less common at retail brokers; leverage is usually delivered through CFDs and spread bets, which are derivatives with their own rules and (for retail) leverage caps. Settlement is T+2 in many markets.
Canada and Australia: margin accounts exist with similar maintenance mechanics; leverage caps for derivatives are set by local regulators.
Crypto: "margin" on an exchange means borrowing from the exchange or other users, with automatic liquidation at a set price; there is no regulator-imposed maintenance level and liquidation can be abrupt.

Everywhere, the lesson is the same: borrowed money has a cost, a collateral requirement, and a lender who will act in their own interest when things go wrong.

Try it: Open your broker's account settings and find out which type you have. If it is margin, find the interest rate and the maintenance requirement. Then take a position you might realistically buy and run the table above for it: at what percentage decline would you be margin-called? Write that number next to the position.

Recap

A cash account uses only settled money; selling and re-buying before settlement causes good-faith violations.
A margin account lets you borrow against holdings, short stock, and trade more option strategies, at the cost of interest and margin calls.
Leverage doubles gains and losses; a margin call can force you out before a position recovers.
Beginners should start with a cash account, or run a margin account as if it were one.
Outside the US, retail leverage is more often delivered through CFDs or derivatives with regulator-set caps.