Understanding Options Trading in Australia: What They Are, How They Work, and What Can Go Wrong

Last reviewed: June 2026

Options are one of those instruments that everyone has heard of and almost nobody uses properly. We get asked about them a lot, usually by clients who have read about covered calls generating income or seen someone on social media brag about 10x returns on a call option trade. And look, both of those things are real. But they are two completely different risk profiles, and confusing the two is where most people come unstuck.

This is a plain-English guide to how options actually work, what the common strategies look like in practice, and, most importantly, what the risks are. We've drawn heavily on the Options Clearing Corporation's official disclosure document (June 2024), which is the standard reference for options risk in the US market. The ASX has its own options market with similar mechanics, and we'll flag the Australian-specific angles where they matter.

What exactly is an option and why would you use one?

An option is a contract. It gives you the right to buy or sell a specific asset at a fixed price before a set date. You pay a premium for that right. That's it. The seller of the option (the "writer") takes on the obligation to perform if you exercise.

Two types. A call option gives you the right to buy. You want this when you think a stock will rise above the strike price before expiry. A put option gives you the right to sell. Useful when you think a stock will fall, or as protection against a position you already hold.

Most people first encounter options as a form of cheap leverage, buying exposure to a stock's move for a fraction of the share price. And that's a legitimate use case. But options are equally useful as hedging tools, income generators (covered calls), and risk management instruments. The problem is that the leverage works both ways, and time is always working against the buyer.

Term	What It Means
Premium	The price you pay to buy the option. If it expires worthless, this is your maximum loss as a buyer.
Strike / Exercise Price	The fixed price at which you can buy or sell the underlying asset.
Expiry	The date the option lapses. After this, it is worthless.
In the money	The option has intrinsic value. A call is in the money when the share price is above the strike.
Out of the money	No intrinsic value. Exercising it would make no financial sense at current prices.
Option Holder	The buyer. Rights only, no obligations.
Option Writer	The seller. Receives the premium, takes on the obligation to perform if exercised.
American-style	Can be exercised at any time before expiry. ASX equity options are American-style.
European-style	Can only be exercised at expiry. Most index options are European-style.

What types of options are out there?

Equity options cover individual stocks and ETFs. Standard contracts represent 100 shares. If you're trading on the ASX, these are what you'll encounter first. They're American-style, meaning you can exercise any time before expiry.

One thing worth knowing here: if a company pays a regular cash dividend, the option terms generally aren't adjusted for it. The covered call writer keeps the dividend, but call holders sometimes try to exercise just before the ex-dividend date to capture it. That creates extra assignment risk for writers heading into dividend season, and it catches people off guard every reporting period.

Index options settle against an index value rather than physical shares. Settlement is always in cash. Because you can't deliver an index, exercise produces a cash payment equal to the difference between the index level and the strike price, multiplied by the contract multiplier. These carry a quirk that equity options don't: trading in the underlying components can continue in after-hours sessions even after the index option has stopped trading. That gap can move the settlement value in a direction you didn't expect.

There are also FLEX options (where counterparties can negotiate non-standard terms), binary options (fixed payout or nothing), and options tied to debt, credit events, or foreign currencies. But for most Australian retail investors, equity and index options are where the action is.

What are the real risks of buying options?

Buying options looks simple. You pay a premium, you can't lose more than that. Both of those things are true. But the ways you can lose the entire premium are more varied than most people appreciate.

Time decay is constant and relentless

An option is a wasting asset. Every single day that passes without the underlying moving in your favour, the option loses value. You have to be right about direction and right about timing. A stock that does exactly what you expected, but three months too late? Total loss. We've seen this trip up more clients than almost any other dynamic in options.

Leverage cuts both ways

The OCC disclosure document illustrates this well. Three investors each start with $5,000. One buys stock directly. One buys a single option contract and parks the rest in T-bills. The third goes all-in on options. If the stock finishes flat or below the strike at expiry, the all-in options investor loses everything. The stock investor is just down 8%. Leverage is spectacular on the way up. On the way down it's brutal, and that's not a word we use lightly.

Cheap options are often just expensive lottery tickets

The further out of the money the option is, the more the underlying needs to move before you break even. Buying cheap options feels like buying cheap insurance. It isn't. The expected value is often terrible. The premium is low because the probability of payoff is low. That's the market being efficient, not generous.

What happens when you write (sell) options?

This is where the risk profile changes dramatically. And it's where most retail investors underestimate what they've taken on.

Covered calls: capped upside, full downside

If you write a call against a stock you own, you collect the premium but forfeit any gain above the strike. Here's the worked example. You own stock at $50, write a call at $50 for a $4 premium. Stock goes to $58 at expiry. You receive $54 all up ($50 + $4) instead of $58. You left $4 on the table. Not a disaster, but definitely something you need to understand before committing to the strategy.

And if the stock falls? You still bear that loss. The premium offsets it, but only partially. We talk to clients who think covered calls are "free money." They aren't. They're a trade-off, selling future upside for current income.

Naked calls: unlimited loss potential

Writing a call without owning the underlying shares is one of the highest-risk positions in finance. Full stop. The OCC gives this example: a writer sells an uncovered call with a $4 premium, the stock jumps to $69. They close the position at a $19 loss per share, netting a $1,500 loss after accounting for the $400 premium received. One trade. One bad week.

Put writing: substantial downside, margin calls

Writing puts means you're committing to buy the underlying at the strike price if assigned. If the stock falls hard, you're buying something worth materially less than what you're paying for it. Cash-secured put writing (depositing cash equal to the exercise price) eliminates the margin call risk, but you're still exposed to the full decline below the strike. The premium helps a bit. Just not enough if the underlying halves.

Strategy	Max Gain	Max Loss	Margin Required?
Buy a call	Unlimited (above strike)	Premium paid	No
Buy a put	Strike minus zero	Premium paid	No
Write a covered call	Premium + strike (capped)	Full fall in underlying	Generally no
Write a naked call	Premium received	Unlimited	Yes
Write a cash-secured put	Premium received	Strike minus zero	No (cash deposited)

How does exercise and settlement actually work?

Most options traders never exercise their options. They close positions by selling the option back into the market. But understanding the mechanics matters, particularly if you're writing.

American-style exercise means the holder can exercise at any point before expiry. As a writer, you can be assigned on any business day from the moment you sold the contract. Once assigned, you can't close the position. You must perform. And you may not find out about the assignment for a day or two after it has occurred. That lag catches people off guard.

European-style exercise means exercise only at expiry. More predictable for writers, but it means holders can't react to favourable moves during the option's life. The only way to realise value before expiry is to sell in the secondary market. Most index options are European-style.

One more thing worth flagging: many brokerage firms have standing instructions to automatically exercise in-the-money options at expiry. If your option expires slightly in the money, the transaction costs of exercise could exceed the cash settlement amount, turning a small win into a small loss. Know your broker's auto-exercise policy, and tell them explicitly if you don't want it to apply.

What other risks should you know about?

Margin requirements move. For uncovered positions, margin requirements aren't fixed. They go up when the market moves against you. The capital you need to maintain a position can increase sharply and quickly, at precisely the moment you can least afford it. We've watched clients scramble to meet margin calls at 7am, and it's never a fun conversation.

Transaction costs add up. An option that's technically in the money may still produce a net loss after commissions and exercise costs are counted. Auto-exercise features can trigger this, which is why knowing your broker's policy matters more than most people realise.

Tax treatment is complicated. Options taxation varies by jurisdiction, holding period, and strategy. Australian tax treatment differs from US treatment. And if you're running a systematic strategy, the ATO's position on whether your gains are capital or income can have a big impact on after-tax returns. This is not an area to wing it. Get specific advice.

Index options are exposed to settlement gaps. If major economic news drops after the options market closes but before settlement, the settlement value can move significantly and you had no chance to act. The position is simply wherever it lands.

What should you actually do with all of this?

Options are genuinely useful instruments. Used well, they can hedge existing positions, generate income on portfolios that are otherwise sitting still, or give you leveraged exposure without the full capital commitment of owning the underlying stock.

But the source material we've drawn from here is specifically focused on what can go wrong. And that framing is appropriate. If you're new to options: start with buying calls or puts before writing anything. As a buyer, the most you can lose is the premium you paid. As a writer, the losses can be significantly larger.

The two rules that trip up most people new to writing options:

First, margin requirements are not fixed and can increase sharply against you. Second, assignment can happen at any time on American-style options, not just near expiry. Both of these create scenarios where your worst day with options is much worse than your worst day owning the shares directly.

We're not anti-options. We use them in client portfolios, particularly covered calls and protective puts for risk management. But we'd rather you understood the full picture before you put capital at risk. The upside of options is well advertised. The downside, less so.

Frequently Asked Questions