FRM Exam Part I · Options Markets

Option Trading Mechanics and Exchange-Traded Options

Updated 11 October 2026 · Fact-checked

Exchange-traded options are standardized contracts traded on an exchange and guaranteed by a clearing house, while OTC options are customized and bilateral. For exam questions, identify the contract terms, adjust strike and contract size for splits, ignore cash dividends in exchange-traded options, and check whether margin applies to the writer.

Understand Option Trading Mechanics and Exchange-Traded Options

An option gives the holder a right, not an obligation. The holder pays a premium. The seller (the writer) takes on the obligation if the holder exercises. This asymmetry drives everything in trading mechanics: only the writer can lose more than the premium, so only the writer posts margin.

Exchange-traded options are standardized. The exchange fixes the underlying, the contract size, the expiration date and the strike prices. For US equity options, one contract covers 100 shares. Standardization makes contracts interchangeable, which creates liquidity and lets traders close positions easily. OTC options are private deals between two parties. Terms are negotiable, so they can match a hedge exactly, but they are harder to unwind and carry counterparty credit risk unless collateralized or cleared.

The clearing house (for example the Options Clearing Corporation in the US) sits between buyer and seller. After a trade, it becomes the buyer to every seller and the seller to every buyer. The buyer and writer no longer face each other, so the buyer does not worry about the writer defaulting. The clearing house manages its own risk through member margin and clearing fund contributions. When a holder exercises, the clearing house randomly assigns the exercise to a member with a short position in that series.

Margin protects the clearing house. The buyer pays the premium in full and posts no margin. The writer of a naked (uncovered) option must post margin that is adjusted daily as prices move. A covered call, where the writer owns the shares, generally needs no margin on the option. Margin on naked equity options is commonly the greater of two calculations, shown below. Margin rules differ by exchange and broker, so in an exam use the formulas given in the question.

Exchange-traded stock options are adjusted for stock splits and stock dividends, but not for cash dividends. After an n-for-m split, the strike falls and the number of shares per contract rises so the position's total value is unchanged. A 2-for-1 split halves the strike and doubles the shares. For a 5% stock dividend, treat it as a 21-for-20 split. Cash dividends cause no adjustment, which is why a large dividend can make early exercise of an American call attractive and lowers call prices.

Key formulas to remember

Split adjustment (n-for-m): New strike = Old strike × m ÷ n; New contracts' shares = Old shares × n ÷ m; In an n-for-m split, you get n new shares for m old. A 3-for-2 split multiplies the strike by 2/3 and shares by 3/2.
Stock dividend as split: x% stock dividend = (100 + x)-for-100 split; A 25% stock dividend is 5-for-4, so strike × 4/5 and shares × 5/4.
Cash dividend adjustment: No adjustment to strike or size for exchange-traded options; Exceptions exist only for very large special dividends, so a standard question assumes none.
Naked equity call margin (US-style, as in Hull): Margin = greater of (1) 100% of option proceeds + 20% of underlying value − out-of-the-money amount, and (2) 100% of option proceeds + 10% of underlying value; Per share, then multiply by contract size. Out-of-the-money amount for a call = max(K − S, 0). Use the percentages given in the question.
Naked put margin (US-style, as in Hull): Margin = greater of (1) 100% of proceeds + 20% of underlying value − out-of-the-money amount, and (2) 100% of proceeds + 10% of exercise price; Out-of-the-money amount for a put = max(S − K, 0).
Contract value: Premium paid = quoted premium × shares per contract × number of contracts; Quotes are per share.

How to solve Option Trading Mechanics and Exchange-Traded Options questions

Use this sequence for any question on trading mechanics, adjustments or margin.

1Classify the market: standardized exchange-traded with a clearing house, or customized OTC with bilateral credit risk.
2Write down the contract terms: underlying, strike, expiry, shares per contract and number of contracts.
3Identify the corporate event: split, stock dividend, or cash dividend. Cash dividends do not adjust exchange-traded terms.
4For a split, convert to n-for-m, then new strike = old strike × m/n and new shares = old shares × n/m. Check that strike × shares is unchanged.
5For margin, identify who posts it: only the writer. Check whether the option is covered or naked.
6Compute both margin tests per share, take the greater, then multiply by shares and contracts.
7Sanity check: does the answer have the right units (per share or per contract) and a sensible size?

Quickest way: Invariant check for splits and margin

When to use it: Use it when the options list close-looking numbers and time is short.

For splits, keep strike × shares constant. Pick the answer where this product equals the original.
For a stock dividend, convert the percentage to a split ratio first.
For margin, compute test 1 and test 2 per share. Test 2 is the floor, so the answer is never below it.
Eliminate any option that gives the buyer a margin requirement or adjusts for an ordinary cash dividend.

Common mistakes in Option Trading Mechanics and Exchange-Traded Options

Adjusting the strike for ordinary cash dividends on exchange-traded options.
Students recall that dividends lower the stock price and assume the contract must compensate.
Fix: Exchange-traded options are protected against splits and stock dividends only. Cash dividends are handled by the market price of the option.
Multiplying the strike by n/m instead of m/n in a split.
The ratio is read upside down.
Fix: Check that the strike falls after a split. A 2-for-1 split halves the strike. Verify strike × shares is unchanged.
Charging margin to the option buyer.
Students confuse options with futures, where both sides post margin.
Fix: The buyer pays the premium in full and has no further liability. Only writers of uncovered positions post margin.
Forgetting to multiply per-share margin by 100 shares and the number of contracts.
Option quotes are per share, so the arithmetic is done at that level and then left.
Fix: Always end with a units check: per share × shares per contract × contracts.
Using the out-of-the-money deduction in the wrong direction.
Call and put formulas look alike.
Fix: Call: max(K − S, 0). Put: max(S − K, 0). The deduction is zero for in-the-money options.
Saying the clearing house takes market risk on the options.
Students read that it guarantees performance.
Fix: It stands between the two parties, so its net position is flat. It bears counterparty default risk, which it controls with margin and member contributions.

Worked examples

Example 1

A trader holds 10 call option contracts on a stock, each on 100 shares with a strike of $60. The company announces a 3-for-2 stock split. What are the new strike and total number of shares covered?

Show the solution

Identify the split: n = 3 new shares for m = 2 old shares.
New strike = 60 × 2 ÷ 3 = $40.
Original shares = 10 × 100 = 1,000. New shares = 1,000 × 3 ÷ 2 = 1,500.
Check the invariant: 60 × 1,000 = 60,000 and 40 × 1,500 = 60,000.

Answer: The strike becomes $40 and the position covers 1,500 shares.

Example 2

An investor writes one naked call contract on 100 shares. The option price is $5, the stock price is $90 and the strike is $95. Using margin rules of the greater of (1) 100% of proceeds + 20% of the underlying value − out-of-the-money amount and (2) 100% of proceeds + 10% of the underlying value, what is the initial margin requirement if the investor has received the option premium separately and counts it within the formula?

Show the solution

Per-share proceeds = $5.
Out-of-the-money amount = max(95 − 90, 0) = $5.
Test 1: 5 + 0.20 × 90 − 5 = 5 + 18 − 5 = $18.
Test 2: 5 + 0.10 × 90 = 5 + 9 = $14.
Greater is $18 per share.
Multiply by 100 shares: 18 × 100 = $1,800.

Answer: The margin requirement is $1,800, including the $500 premium received, so $1,300 of additional funds is needed beyond the premium.

Exam tips

Expect numeric split adjustments. Practice n-for-m and stock dividend conversions until the strike × shares check is automatic.
Know which events adjust the contract: splits and stock dividends yes, ordinary cash dividends no.
Questions on the clearing house test the idea that it is the counterparty to both sides and removes bilateral credit risk. Only OTC trades carry it, unless centrally cleared.
For margin, read which percentages the question gives. Do not rely on remembered values if the stem supplies different ones.
Be ready to contrast exchange-traded and OTC options on standardization, liquidity, flexibility and credit risk.

Practice questions from Options Markets

Option Trading Mechanics and Exchange-Traded Options in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Option Trading Mechanics and Exchange-Traded Options: frequently asked questions

What is the main difference between exchange-traded and OTC options?

Exchange-traded options are standardized in strike, expiry and size, and are guaranteed by a clearing house. OTC options are customized between two parties and carry counterparty credit risk unless collateralized or cleared. Standardization gives exchange options better liquidity.

Who has to post margin on options?

The option writer posts margin when the position is uncovered, because the writer faces potential large losses. The buyer pays the premium upfront and has no margin requirement. A covered call generally needs no extra margin on the option.

How are exchange-traded options adjusted for stock splits and dividends?

A split lowers the strike and raises the number of shares so total value is unchanged. A stock dividend is treated as a split, for example a 20% stock dividend is a 6-for-5 split. Ordinary cash dividends do not adjust the terms.

What does the options clearing house do?

It becomes the buyer to every seller and the seller to every buyer, so the two original parties do not face each other. It collects margin from members and randomly assigns exercises to short positions. This removes counterparty risk for the holder.