Options — The Right But Not the Obligation

The Right, But Not the Obligation

An option is a contract that gives its buyer the right — but not the obligation — to buy or sell an underlying asset at a fixed price, called the strike price, on or before a specific date, called the expiry. In exchange for that right, the buyer pays the seller an upfront fee called the premium. If the trade never becomes worth using, the buyer simply lets the option expire and loses the premium. Nothing more is owed.

That single phrase — right, not obligation — is the entire reason options exist as a distinct product rather than just a smaller version of a future. With a future or a forward, both parties are locked into the trade happening, for better or worse. With an option, only one party is locked in: the seller (also called the writer). The buyer has a choice, and that choice has value, which is exactly what the premium is paying for.

There are exactly two types of option, and everything else in this chapter is really just variations and combinations of these two building blocks.

From here, every option strategy — covered calls, protective puts, spreads, straddles, cash-secured puts — is simply a different combination of buying and/or selling calls and puts at different strikes and expiries. Understanding these two shapes properly is worth more than memorising twenty strategy names.

The Vocabulary You Need First

Options trading has a dense vocabulary, and most of the confusion people run into is really just unfamiliarity with these terms rather than the underlying concept being hard. Here is the full set you need before anything else makes sense.

Calls in Depth — A Worked Example

Say a share trades at £50. You believe it will rise over the next three months, but you don't want to commit the full capital of buying 100 shares outright (£5,000). Instead, you buy a call option with a £52 strike, expiring in three months, for a premium of £1.50 per share — since UK and US options typically represent 100 shares per contract, that is £150 total for one contract (100 × £1.50).

Your break-even point is the strike plus the premium: £52 + £1.50 = £53.50. Below that price at expiry, you lose some or all of your £150 premium. Above it, every pound the share rises past £53.50 is profit, multiplied by 100 shares per contract. If the share rises to £60, your option is worth at least £8 per share intrinsic value (£60 − £52 strike) — £800 for the contract — against a £150 cost, a profit of £650, roughly 433% on the capital risked. The same £150 spent buying actual shares at £50 would have bought you three shares, worth £180 at £60 — an £30 profit. The leverage inherent in the option is exactly what produces both the outsized gain if you're right, and the total loss of the £150 if you're wrong and the share never reaches £52.

This is the appeal of buying calls: a defined, limited maximum loss (the premium) against a theoretically unlimited gain if the underlying keeps climbing. It is also the trap: because premiums decay toward zero as expiry approaches (covered below), being right about direction but wrong about timing can still lose you the entire premium.

Puts in Depth — Insurance, Not Just a Bet on a Fall

Puts work in reverse. If you hold 100 shares of a company at £50 and you're worried about a near-term drop — ahead of an earnings announcement, for instance — you can buy a put with a £48 strike, expiring in one month, for a premium of £1.20 per share (£120 for the contract). If the share falls to £35 on bad news, your shares are worth £1,500 less than when you bought the put, but the put itself is now worth at least £13 per share intrinsic value (£48 − £35) — £1,300 for the contract — almost entirely offsetting the loss on your shares, at a cost of just £120. This is a protective put: effectively buying insurance on a holding you already own, with the premium as your insurance cost and the strike as your floor price.

If instead you don't own the shares and simply buy the put speculatively, expecting the price to fall, the mechanics are identical but the purpose is pure speculation rather than insurance: you profit if the share falls below the strike minus the premium (£48 − £1.20 = £46.80), and you lose the full £120 premium if it doesn't.

Puts are also the key reason options get described as a tool for managing downside risk rather than purely for speculation. A long-term investor who doesn't want to sell a position (perhaps for tax reasons, or because they remain convinced of the long-term thesis) but who wants temporary protection against a specific, foreseeable risk — a product recall, a regulatory decision, an election — can buy puts covering just that window, then let the protection lapse once the risk has passed.

The Payoff Diagram — Why Buyers and Sellers Are Not Mirror Images

The single most useful mental picture in options trading is the payoff diagram: profit or loss on the vertical axis, the underlying price at expiry on the horizontal axis. Plotted this way, a few shapes repeat throughout every options strategy, and once you can see them in your head, most strategies become far less mysterious.

Buying a call produces a flat line at −£150 (the premium) for every price below the £53.50 break-even, then a line rising at £100 of profit for every £1 the share rises above that point, with no ceiling. Buying a put is the mirror image on the downside: flat at −£120 for every price above the £46.80 break-even, rising as the price falls, capped only because a share price cannot go below zero.

Now flip to the seller's side of exactly the same contracts, and the picture inverts completely rather than simply mirroring. Selling a call produces a flat profit line at +£150 (the premium received) for every price below £53.50 — the seller keeps the premium and nothing is exercised — but below that point, for every £1 the share rises further, the seller loses £100, with no ceiling on how far the price (and therefore the loss) can rise. Selling a put produces a flat profit at +£120 above £46.80, but losses that grow, pound for pound, all the way down to a share price of zero.

The asymmetry to notice: buyers have capped, known losses and uncapped or very large potential gains. Sellers have capped, known gains (the premium, and nothing more, ever) against uncapped or very large potential losses. This is not a flaw in the contract — it is the defining structural feature of options, and it is the single most important thing to understand before placing a real trade on either side.

Selling Options — Why People Do It Anyway

Given the risk profile above, it might seem like selling options is simply a bad idea. In practice, selling options is an enormous and legitimate part of the market, because two specific variants manage the unlimited-loss problem directly by tying the sale to an asset the seller already has, or is already willing to buy.

A covered call means selling a call option on shares you already own. If the share price rises above the strike and the call is exercised, you simply sell the shares you already hold at the strike price — a sale you were, by definition, already willing to make. You keep the premium regardless of outcome, and your only "loss" relative to doing nothing is missing out on gains above the strike price, not an open-ended cash loss. This is one of the lower-risk, income-generating options strategies and is widely used by long-term holders willing to cap their upside in a stock in exchange for steady premium income.

A cash-secured put means selling a put option while holding enough cash to buy the shares at the strike price if assigned. If the share falls below the strike and the put is exercised, you simply buy the shares at the strike price — a price you had already decided you were happy to pay, with the premium received effectively reducing your purchase cost. If the share stays above the strike, you keep the full premium and walk away. This is commonly used by investors who want to buy a share "if it gets cheaper," and get paid a premium for stating that intention in advance.

Time Decay — The Clock Nobody Can Stop

Every option, no matter how it behaves otherwise, loses time value as expiry approaches, all else being equal. This effect is called theta, and it is one of the "Greeks" — a set of measures options traders use to describe how an option's price reacts to different factors. Theta is not linear: time decay accelerates sharply in the final weeks and days before expiry, which is why an option that looked cheap and full of potential a month out can be worth nearly nothing with three days left, even if the underlying hasn't moved much at all.

This has a direct practical consequence that catches new options buyers out repeatedly: being right about the direction of a move is not enough. You also have to be right about timing. A trader who buys a call expecting a share to rise over the following year, but picks an option expiring in three weeks, can watch the share actually rise six months later — and lose the entire premium anyway, because the option expired long before the move happened. Buyers are, in a very literal sense, fighting the clock as well as the market.

Sellers benefit from exactly the same mechanic working in reverse: every day that passes without the underlying moving against them is a day of time value decaying in their favour, which is the structural reason covered calls and cash-secured puts can generate steady income over time even without the underlying moving much at all.

Spreads — Trading the Shape, Not Just the Direction

Buying or selling a single option is only the simplest version of an options trade. A spread combines buying one option and selling another, usually on the same underlying and expiry but at different strikes, and spreads exist specifically to reshape the risk and cost profile of a pure directional bet, often at the expense of giving up some potential upside.

A bull call spread — buying a call at a lower strike and simultaneously selling a call at a higher strike, both with the same expiry — reduces the net premium paid (because the premium received from selling the higher-strike call partially offsets the cost of buying the lower-strike one), but also caps the maximum profit at the difference between the two strikes, minus the net premium paid. Using the earlier example, buying a £52 strike call for £1.50 while selling a £58 strike call for £0.60 brings the net cost down to £0.90 per share (£90 for the contract), but caps the maximum profit at £6 per share minus the £0.90 net premium — £5.10, or £510 for the contract — no matter how high the share price eventually rises. The trade-off is explicit: lower cost and lower break-even, in exchange for giving up unlimited upside.

A bear put spread works the same way in reverse for a bet on a fall, and credit spreads (selling the more expensive option and buying a further-out-of-the-money option as protection) are a common way to collect premium income while capping the open-ended loss that a naked short position would otherwise carry — directly addressing the uncapped-risk problem covered earlier in this chapter, at the cost of also capping the maximum premium collected. For a retail trader specifically concerned about the unlimited-loss risk of naked option selling, a credit spread is often a more appropriate structure than selling the same option uncovered, since the defined maximum loss makes position sizing and risk management considerably more straightforward.

Exercise Styles and Assignment

Whether you can exercise an option before expiry depends on its style. American-style options — the standard for most individual US and UK single-stock options — can be exercised at any time up to and including the expiry date. European-style options — the standard for most index options, including FTSE 100 index options — can only be exercised exactly on the expiry date itself, never before. Despite the names, this has nothing to do with geography; both styles trade in both regions.

In practice, most options buyers never actually exercise at all — they simply sell the option itself back into the market before expiry if it has value, which achieves the same economic profit without the extra step of taking delivery of shares or cash. Exercise and assignment matter most for option sellers, who need to understand that being assigned can happen at any point before expiry for American-style options (if the option is sufficiently in the money), not only on the final day, which is why covered call and cash-secured put sellers should always be mentally prepared for early assignment rather than assuming it will only happen at expiry.

The Other Greeks, Briefly

Theta is only one of several "Greek" measures used to describe how sensitive an option's price is to different factors, and while a full treatment belongs in more advanced material, knowing roughly what each one represents helps make sense of options data on any broker platform.

Delta measures how much an option's price moves for a £1 move in the underlying — a call with a delta of 0.60 gains roughly £0.60 in value for every £1 the underlying rises. Delta also roughly approximates the probability the option finishes in the money, which is why deeply in-the-money options have deltas approaching 1.0 (behaving almost like owning the underlying directly) and deeply out-of-the-money options have deltas approaching zero. Gamma measures how quickly delta itself changes as the underlying moves, and tends to be highest for at-the-money options close to expiry — exactly the point where small price moves can swing an option between worthless and valuable most dramatically. Vega measures sensitivity to changes in implied volatility, directly relevant to the IV crush effect covered above.

None of these need to be calculated by hand — every broker platform offering options displays them directly alongside the price — but recognising the terms, and roughly what each one is pointing at, makes it considerably easier to understand why two options with the same strike and expiry can behave very differently as market conditions shift around them.

Trading Options in the UK

Standard Stocks and Shares ISAs in the UK do not permit options trading — the tax wrapper is built around holding shares, funds, and bonds directly, not derivatives. To trade listed options, you need a general investment account (also called a dealing account) or a specialist derivatives trading account, and most UK brokers require an additional application process and demonstration of relevant experience before granting options trading permissions, reflecting how differently regulators treat this asset class compared to buying a share or a fund.

This is also where UK retail investors sometimes confuse options with spread betting and CFDs, which achieve superficially similar directional exposure through a very different legal and tax structure. Spread betting in the UK is technically structured as a bet rather than an investment, which (at time of writing, and subject to change) means profits are free from capital gains tax and income tax for most UK residents — but spread bets and CFDs carry their own leverage and negative-balance risks covered fully in the leverage chapter, and are not the same product as a listed option, even when used to express a similar market view.

FCA rules also restrict the marketing of certain high-risk derivative products to UK retail consumers more tightly than in some other jurisdictions — for example, the sale of certain complex derivative products linked to crypto-assets has been banned outright for retail clients since 2021 — so it is worth checking the FCA register and current restrictions directly before assuming a product is available to retail accounts simply because a broker lists it.

Common Mistakes Retail Options Traders Make

Buying far out-of-the-money options because they're cheap. A £0.10 option looks like a lottery ticket with huge potential upside, but deeply out-of-the-money options require a large, fast move to pay off at all, and the overwhelming majority expire completely worthless. Cheap is not the same as good value.

Ignoring time decay when choosing an expiry. Buying the cheapest, nearest-dated option to maximise percentage leverage is a common beginner instinct, and it is also the single easiest way to be right about direction and still lose the entire premium, because there simply wasn't enough time left for the move to happen.

Selling naked options without understanding the uncapped risk. Collecting a £150 premium feels like easy, repeatable income — until a single large adverse move produces a loss that wipes out dozens of previous winning trades at once. Naked selling strategies have a statistically high win rate on any individual trade and a small number of catastrophic losses that account for most of the total return — in the wrong direction.

Trading options on illiquid underlyings. Options on small, thinly-traded companies often have wide bid-ask spreads, meaning you can lose a meaningful percentage of your position simply on entering and exiting the trade, independent of whether your market view was even correct.