Expiration Dates and Theta (Time Decay)

Every listed option has an expiration date, the last day the contract is active under standard rules. For many U.S. equity options, that day is a Friday. After expiration, the contract ceases to exist. What remains for in-the-money options is intrinsic value only, paid through exercise or cash settlement depending on product and broker process.

Time is a resource with a price. Option buyers pay for days left. Option sellers often collect that payment and face other risks. The Greek theta names how much value tends to erode as one day passes, holding stock price, IV, and other inputs roughly flat.

What happens at expiration

In the money (ITM) at expiry:

• Long calls may be exercised or auto-exercised per broker rules, converting to long stock or cash settlement.
• Long puts may convert to short stock or cash settlement.
• Short options may be assigned.

Out of the money (OTM) at expiry:

• Long options expire worthless (loss = premium paid).
• Short options expire and keep premium collected.

Read Assignment and exercise before you sell options. Pin risk near the strike on expiration week can surprise traders who ignore gamma.

Theta in plain English

Theta is usually quoted as change per one day. A call showing theta −0.05 might lose about $0.05 per share ($5 per contract) from one calendar day, if nothing else moves.

Long options typically have negative theta (you lose from time). Short options typically have positive theta (you gain from time) but carry assignment and margin risk.

Full treatment: Theta explained. Visualize decay in Greeks in the builder by sliding the valuation date toward expiry.

Why decay is not linear

Extrinsic value does not melt at a constant daily rate for most of the life. Far from expiration, theta per day is often smaller. In the final weeks, especially the last week, decay can accelerate on ATM options.

That is why holding OTM lottery tickets into expiration week is dangerous even if your thesis is eventually right but slow.

Weeklies vs monthlies vs LEAPS

Weeklies: Short clock, cheaper upfront, fast theta. Useful for tactical trades, harsh on slow moves.

Standard monthlies: Middle ground, liquid on large caps.

LEAPS (long-dated): More time, higher premium, slower daily theta early on, still loses extrinsic eventually.

Calendar spread strategies buy a longer dated option and sell a shorter dated option to express a view on timing and decay differences.

Tie-in to delta and IV

Time decay hits extrinsic value. Intrinsic vs extrinsic value splits the premium.

Near expiry, delta on ATM options can swing quickly (gamma). A $100 stock hovering at a $100 strike on Friday can flip a call from OTM to ITM with a small tick. See Delta explained.

IV can shrink faster than theta alone explains around events. Pair this guide with Implied volatility basics and Vega explained.

Worked example 1: long call losing to theta

XYZ at $100. You buy the $100 call for $5.00 with 30 days left. All $5 is extrinsic (ATM).

Scenario A: Two weeks pass, stock still $100, IV unchanged. Call might trade near $3.00. You lost about $2 from theta without the stock falling.

Scenario B: At expiration, stock $100. Call is $0. You lost the full $5 ($500 per contract).

Scenario C: At expiration, stock $106. Intrinsic $6, profit about $1 per share after $5 premium. Theta hurt you until the move arrived in time.

Worked example 2: short put collecting theta

XYZ at $100. You sell the $95 put for $2.00 ($200 credit), 45 days left.

• If XYZ stays above $95 through expiration, you keep $200 minus fees (best case).
• If XYZ is $98 at expiry, put intrinsic is $0, you still keep full premium if OTM.
• If XYZ is $90 at expiry, you may be assigned and buy stock at $95 while market is $90 (stock loss partially offset by $200 credit).

Positive theta helped daily while the stock cooperated. Delta and assignment risk still matter. This is not "free money."

Reading decay on payoff charts

How to read an options payoff chart shows the final angular shape. In the builder, move the valuation date slider: the live curve settles onto the expiration line. That visual is theta plus changing delta in action.

Choosing an expiration on purpose

Match expiration to your thesis window:

• Earnings play: often includes the event date inside the option life.
• Swing trade: enough days for the move, not so many that theta dominates.
• Hedge on stock: often buy puts expiring after the risk window you fear.

Strike price and moneyness interacts with decay: ATM burns extrinsic fastest in dollar terms near the end; OTM can burn in high percentage terms.

Standard monthly vs quarterly cycles

Large caps list monthly expirations and often weeklies. Index products may use different calendars. Always confirm the exact expiry timestamp (AM vs PM settlement) on your broker help page. Theta accelerates into that final session, not only on the calendar Friday label.

Ex-dividend and early assignment

Short ITM calls before ex-dividend can face early assignment when the dividend exceeds remaining extrinsic. Long stock plus short call (covered call) holders may deliver shares and miss the dividend if assigned. Time decay helped until assignment risk spiked.

Holding through expiration week

Many traders reduce size or close long OTM options before the last five sessions because gamma and theta together magnify swings. If you keep a lottery ticket, know the dollar risk is still 100% of premium unless you sell early.

Common mistakes

• Buying short-dated OTM calls without a catalyst timeline.
• Assuming theta is constant every day.
• Forgetting assignment on short ITM options into expiry weekend.

Related guides

• What are options?
• Call options explained
• Put options explained
• Greeks in the builder

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ThetaViz provides educational tools only. This guide is not investment, tax, or legal advice. Prices, margin requirements, and tax rules change. Confirm details with your broker and qualified professionals before trading.