Expiry: the day your option dies

Why is this important?

Lesson 5 showed you that most of an option's premium is time value: payment for what might still happen before a deadline. That deadline has a name: expiry. And expiry isn't a vague idea, it's a specific date printed right there in the contract, ticking down every single day whether you're watching or not.

Get expiry wrong and you can do everything else right and still lose. You could pick the correct direction, the correct strike, and still watch your option die worthless because you ran out of time before the move arrived.

Real market example

India runs several expiry schedules, and mixing them up is a genuine beginner trap:

• NIFTY weekly options expire every Tuesday (this moved from the historic Thursday in late 2025; exchanges do revise expiry days from time to time, so always check the current NSE schedule before trading).
• NIFTY monthly options expire on the last Tuesday of the month.
• BSE's Sensex options expire on Thursday.

Take our familiar 25,000 CE, bought at ₹120 for ₹7,800 a lot. Suppose it's a weekly option and Tuesday arrives with NIFTY sitting at 24,950, below the strike.

Full loss: ₹7,800. Now the win case, same trade, different Tuesday: NIFTY closes at 25,180.

Net profit ₹3,900. Notice the premium collapsed to exactly the intrinsic value in both cases: ₹0 and ₹180. All the time value that existed a week earlier has completely evaporated by the closing bell. That's what expiry means for a premium: it stops being intrinsic-plus-hope and becomes intrinsic, full stop.

Because NIFTY options are cash-settled, nothing is delivered: profit or loss is simply credited or debited in rupees. Stock options are different: they end in physical delivery of shares, which has surprised more than one beginner with a margin call they didn't expect.

Key concepts

• Expiry: the fixed date and time an option contract stops existing. After this, it either pays out its intrinsic value or is worth ₹0.
• DTE (days to expiry): the standard shorthand traders use for how much time is left. "7 DTE" means seven calendar days until the contract dies.
• European-style exercise: Indian index options can only be exercised at expiry, not any day before. This surprises people who expect to "cash in" mid-week like a movie ticket.
• You can always sell before expiry: European style restricts exercising, not selling. You can close your position any second the market is open, and almost everyone does exactly that rather than holding to the final bell.
• Cash settlement vs physical delivery: index options (NIFTY, Sensex) settle in cash automatically. Stock options settle in actual shares, which can mean unexpected delivery obligations and margin requirements.
• Settlement price: what your payout is actually measured against. For NIFTY it is not the 3:29 print but the weighted average of the index over the last 30 minutes, so holding to the bell means accepting a number nobody can see in advance.
• STT on exercise: an option left to expire in the money is taxed differently from one you sold. On index options that difference is now trivial; on stock options it is the single most expensive thing in this lesson.

Visual explanation

Below is the same ATM option's time value, tracked every day from 30 days out down to zero. Watch the curve: it drifts down gently at first, then gets noticeably steeper as expiry approaches. The final week melts faster than the two weeks before it combined.

How traders use it

Choosing an expiry date is choosing how much time you're renting, and it shapes every decision after entry.

• Buyers need the market to move and to move soon. A buyer thinking "I just need two more days" has usually already lost: the decay in those final two days is the steepest of the whole curve.
• Sellers often deliberately target the last week on purpose, collecting premium precisely because it decays fastest against the buyer during that stretch.
• DTE becomes the first filter in strike and strategy selection: before direction, before strike, traders ask "how much time am I buying or selling?"
• Rolling a losing position to a later expiry is really just buying more time value at a fresh price. It doesn't erase the original problem.

The expiry-day traps

Everything above is what expiry is. This is what expiry does to Indian traders who let the last hour arrive on its own.

Trap 1 — the myth, corrected. You will read on a hundred websites that letting an ITM option expire triggers STT on the entire contract value. That was true, and ruinous, until September 2019. Today, exercised index options are charged 0.125% of intrinsic value, against 0.1% of premium if you sell instead. On our 25,000 CE finishing at 25,180, that is ₹14.63 versus ₹11.70. A real difference, and not a reason to panic out of a position.

Trap 2 — the settlement price you cannot see. The genuine reason to square off before 3:30 on an index option is that expiry settles against the average of the last thirty minutes, not the price on your screen. Hold to the bell and you swap a price you can act on for an average you can only accept.

Trap 3 — stock options, where the real money goes. Physically settled contracts are a different animal. Take a Reliance 1,400 CE, lot 500, with the stock at ₹1,405 on expiry day. Intrinsic value: ₹5 × 500 = ₹2,500.

On physical settlement, STT is charged like a delivery trade — on the whole ₹7 lakh, not on your ₹2,500 of profit. Several brokers add a special physical-settlement brokerage on top. A profitable option can and does settle into a net loss.

Trap 4 — the expiry-week margin ramp. From about four days before expiry, exchanges stack delivery margins on ITM stock-option positions in steps, rising steeply each day toward the full value of the shares. A position that needed ₹40,000 on Monday can demand several lakh by Thursday, purely because it might become delivery. Brokers routinely square off clients who cannot fund it — see Lesson 12 for how that ends.

Trap 5 — "I'll just let it lapse." A "do not exercise" facility for close-to-the-money stock options used to exist and was withdrawn. Assume every ITM stock option at the bell settles physically, and check your broker's current expiry-day policy rather than a forum post.

The do-nothing checklist, then, in one line each:

• Index option, OTM at the bell: nothing happens, nothing is owed, no action needed.
• Index option, ITM at the bell: cash is credited automatically against the 30-minute average. Fine, if you accepted that average deliberately.
• Stock option, ITM at the bell: you are buying or delivering shares. Fund it, or close the position by Wednesday of expiry week — not at 3:25 on Thursday, when the only bid left is a bad one.

Common mistakes

• Buying expiry-day options because they're "cheap." They're cheap because the clock has almost run out, not because they're a bargain.
• Confusing "European style" with "can't sell early." You can sell any time the market is open. Only exercising is restricted to expiry.
• Forgetting stock options deliver shares. A stock option left open into expiry, in the money, lands you actual shares, a delivery-margin ramp through the final four days, and STT on the whole contract value rather than on your profit.
• Repeating the STT myth in the wrong direction. Panic-selling every index option because "STT eats the full contract value" has been wrong since 2019. Sell before the bell for the settlement-price reason, not the tax one.
• Assuming decay is a straight line. The curve is steeper near expiry, not constant: the last few days lose more time value than an equal stretch further out.
• Not checking the current expiry day. Weekly expiry moved from Thursday to Tuesday for NIFTY in late 2025. Exchanges revise these schedules; always verify before placing a trade.

Quiz

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