Risk management

How CFDs Work Under the Hood: Leverage, Margin, and Risk

Astron Team · 09/24/2026 · 4 min read

A CFD (contract for difference) is an agreement between two parties — the trader and the broker — to exchange the difference between an asset's value when the position is opened and when it's closed. Neither party ever actually owns the asset: the contract exists only to reflect that price change. Understanding this mechanism from the inside helps you see where the risk comes from, which tends to be bigger than the simplicity of the trading interface suggests.

Where leverage comes from

Leverage exists because the broker requires only a fraction of the position's total value as collateral — the margin — instead of the full amount. If the required margin is 10% and you want to control a R$ 5,000.00 position, you need to deposit R$ 500.00. That 10-to-1 ratio is the leverage: a small move in the asset's price, calculated on the total value of the position, produces a proportionally much larger result on the amount deposited.

The math that shows the effect from the inside out

With the R$ 5,000.00 position from the example above (R$ 500.00 margin), an 8% drop in the asset produces a R$ 400.00 loss — 80% of the deposited margin, even though the asset fell less than a tenth of its value. A 10% drop would wipe out the entire margin. This multiplying effect is at the core of what makes CFDs a high-risk instrument: the percentage change in the asset and the percentage change in your capital stop being the same thing.

What a margin call is

When a position's losses get close to the amount deposited as margin, the broker may issue a margin call — a request to deposit more capital to keep the position open. If that doesn't happen in time, the position is usually closed automatically by the broker itself, even against the trader's wishes, to prevent the loss from exceeding the capital available in the account. This mechanism protects both parties, but it means the trader can be forced out of a position at the worst possible moment, with no control over the timing of that exit.

The cost of keeping leverage open

Besides price risk, keeping a leveraged CFD open overnight usually generates a financing cost (rollover), since, in practice, part of the position's value is being financed. On a R$ 5,000.00 position with a 0.02% daily rate, the cost is R$ 1.00 per day — small on its own, but it adds up on positions held for weeks or months, eating into the result even if the asset's price doesn't move much.

Why CFDs amplify gains and losses equally

It's common to hear about leverage's upside and forget that it works symmetrically. In the earlier example, if the asset had risen 8% instead of falling, the gain would also be R$ 400.00 on the R$ 500.00 margin — an 80% return. Leverage doesn't pick a side: it multiplies the outcome of any move, in whichever direction it happens, which is exactly why it can hand back quick gains and take capital away just as fast.

Why the contract's term matters less than in other instruments

Unlike an option, which has an expiration date and loses time value, a CFD can be held open indefinitely — what changes is the rollover cost, charged every day the position stays active. That makes CFDs, in theory, flexible for varying time frames, but that same flexibility can lead to keeping a losing position open longer than planned, piling up rollover cost on a loss that maybe should have been closed earlier.

What to take from this mechanism

Before trading CFDs, it's worth simulating different drop scenarios for the asset (not just gains) and calculating what that would mean for the deposited margin — not for the position's total value. This simple exercise usually reveals that the real risk of a leveraged position is much bigger than it looks when you only glance at the amount invested on screen. Understanding this mechanism from the inside, before trading, is what separates using leverage in a calculated way from simply accepting the maximum amount offered by the broker without understanding what it represents in risk.