Calls, Puts and Who Owes Whom

Rights, obligations, and the two halves of a premium

An equity option is a contract on 100 shares in which one party holds a right and the other an obligation. A call buyer holds the right to buy at the strike before expiry and pays a premium for it; the call seller collects that premium and takes on the obligation to deliver the shares if the buyer exercises. A put is the mirror: its buyer holds the right to sell at the strike, and its seller is obliged to buy. That asymmetry is the shape of every option payoff: the buyer risks the premium and keeps the upside, and the seller keeps the premium and carries the risk. The premium has two parts, and separating them is what keeps the rest of this subject from becoming a collection of names. Intrinsic value is what the contract is worth if exercised right now: for a call, the stock price less the strike, floored at zero; for a put, the strike less the stock price, floored at zero. Everything above that is extrinsic value — time value and the market’s price for the possibility of movement — and it is the part that decays to zero by expiry. A contract that is deeply in the money is mostly intrinsic and moves almost one-for-one with the shares; a contract that is far out of the money is entirely extrinsic, and it either acquires intrinsic value before expiry or expires worthless. Two consequences follow immediately and they explain most of what happens to retail option positions. First, the extrinsic share is what a buyer is paying for time, and it is a payment that is lost whether or not the direction is right; that is the subject of O4. Second, break-even at expiry is the strike plus the premium for a long call and the strike less the premium for a long put, so the position needs a move to have paid for the extrinsic before it has made anything — which is the difference between being right about the stock and making money on the option. One stock, two contracts, one strike — Call: strike $100, premium $6.20, stock $105: Intrinsic $5.00 + extrinsic $1.20 · Put: strike $100, premium $1.10, stock $105: Intrinsic $0.00 + extrinsic $1.10 ← · Call break-even at expiry: $106.20 — strike plus premium · Realised volatility below implied: The extrinsic is lost: the contract bleeds to intrinsic ← American-style equity options can be exercised any day before expiry, but exercise surrenders the extrinsic value, so the usual way to realise a gain is to sell the contract. Exercise becomes rational when the extrinsic left is smaller than the benefit of holding the shares — a dividend just before expiry is the classic case.

Where the premium comes from: moneyness and time

The size of the extrinsic premium depends on how far the strike is from the price, how much time is left, and how much movement the market expects. Distance matters in a way that is easy to feel and worth stating: an at-the-money contract has the most extrinsic value, because that is where the uncertainty is greatest and where a small move changes the intrinsic value most, while contracts far out of the money have little extrinsic in absolute terms and a large one relative to their price. That is the arithmetic behind the lottery-ticket perception — a cheap far out-of-the-money contract is cheap because the probability of it acquiring intrinsic value before expiry is small, and the market knows it. Time matters through its square root rather than linearly, which is why a three-month option does not cost three times a one-month option. Movement is the third input: when the market expects more volatility, every extrinsic premium is larger, so the same strike costs more, and a strategy that sells premium is being paid more for the risk it takes. None of these is a direction forecast, and it is worth being explicit — a premium is a price for uncertainty over a period, not a statement about where the stock will be. • The buyer holds a right and risks the premium; the seller carries the obligation. • Premium = intrinsic + extrinsic; only extrinsic decays. • At-the-money contracts carry the largest extrinsic value; far out-of-the-money ones carry the least in absolute terms. • Extrinsic value grows with roughly the square root of time and with expected volatility. • Break-even at expiry includes the premium, so direction alone is not enough. The most common first mistake is to buy the cheapest contract because it offers the largest percentage move. It is cheap because its probability of paying is small, so the position is a bet that the market has mispriced a low-probability event — which is a legitimate strategy only with a reason and a sample size, not as a default.

Who is actually on the other side

You do not hold a contract with the person who sold it to you. The moment your trade clears, the **Options Clearing Corporation** is substituted as the seller to every buyer and the buyer to every seller. That substitution is called **novation**, and it is why an option is not a private wager: if the specific counterparty you traded against fails tomorrow, your contract still stands, and the OCC collects margin from its member firms precisely so that it can say that without qualification. Novation works only because the contracts are standardised. Every equity option is 100 shares, a listed expiration, and a strike from a published grid, which means any holder can close any position by trading against the market rather than by hunting down whoever wrote it. **Fungibility is the product.** It is also why a contract can be quoted continuously with a bid and an ask at all: an option is not a bespoke agreement between two parties, it is a unit that any participant may own, and the price of that unit is the price of the risk it carries. The place this machinery surprises holders is expiry, because exercise is not something a long holder has to ask for. An in-the-money contract that retains any value at the close is exercised automatically, by a margin of a single penny, unless the holder instructs the broker not to. A long call therefore finishes the weekend as shares bought at the strike, funded by cash the holder may not have set aside; a short leg finishes as an obligation to deliver shares the writer may not own. That is why every lesson in this subject ends with a plan for the position rather than a hope about the direction. • The OCC novates: it becomes the buyer to every seller and the seller to every buyer. • Standardisation (100 shares, listed expiry, published strikes) is what makes contracts fungible — and therefore quotable. • Exercise is automatic for anything in the money: the default is delivery, not expiration to zero. • A corporate action can produce an adjusted deliverable that is not a round 100 shares, which is covered in the chain lesson. Cash-settled index options and physically settled equity options are different instruments wearing the same words. Index options settle in cash and never hand anyone a share; equity options deliver stock. Read the settlement line on the contract before assuming which one you hold.

Where the choice set comes from

You do not choose from an infinite menu of contracts; you choose from one the exchange has listed, and the listing rules decide which structures are even possible. Equity options sit on a grid of expirations and strikes. The expirations follow a cycle: a near-term series every week, a monthly series expiring on the third Friday, and long-dated series running two or three years out. Because the monthly contracts attract the deepest flow, an option that was once a monthly becomes a quarterly reference and then a leap, which is why the same strike can be available at one date and absent at the next. The strike grid is the other half of the choice set, and it widens as it moves away from the price. Near the money, strikes are listed in small increments; a strike a third above or below the stock may be listed only every five or ten dollars. That matters more than it sounds, because a structure needs two strikes a specific distance apart: a one-dollar-wide vertical cannot exist where the spacing is five dollars, and a butterfly needs three strikes in a row to be listed at all. Spacing therefore constrains the *idea* rather than merely the price, which is why the chain lesson treats it as a pre-trade check. Every contract also carries an identifier — a root, the expiry encoded, and a strike code — so that two contracts that look identical in a broker’s list can be told apart by the exchange, the expiration convention and the settlement terms. The practical reason to care is that adjustments are read off that identifier. When a company splits or spins off a division, the outstanding contracts are not relabelled as something new: their deliverable is adjusted, often to a mixture of stock and cash that is not a clean hundred of one name, and the code is the only place the change is written. A contract originally drawn on a hundred shares can end up delivering a hundred and thirty-seven of one company and cash for the fraction. The takeaway is that the instrument is standardised on purpose, and the standardisation is what makes it quotable and closable. But standardisation is a manufacturing decision, so the first thing to establish about a contract is which one it is: what expiry convention it belongs to, what the strike spacing around it allows, and what it actually delivers. A structure is tradeable only if the exchange has listed the pieces it needs, and safe only if the holder has read what those pieces promise. • Expiry cycles: weekly series, monthly third-Friday contracts, and long-dated series — depth is greatest at the monthly. • Strike spacing widens away from the price, so it constrains which spreads can be built. • The contract identifier encodes the root, the expiry and the strike, and it is where adjustments show up. • A corporate action adjusts the deliverable rather than replacing the contract: not always a hundred shares. • Standardisation is why a contract is quotable; the listing rules are why your structure does or does not exist. The menu is manufactured, so questions about which structures are possible are questions about listing rules rather than about the market’s opinion. Check the grid before designing the payoff.

Sources

• Option contract mechanics and settlementCBOE educational materials on equity options
• Premium decomposition and early exerciseHull, “Options, Futures, and Other Derivatives”
• Assignment and exercise statisticsOptions Clearing Corporation educational publications