Foundations

Expiry Date

The expiry date is the day an option contract ceases to exist and is settled — Indian index options have weekly and monthly expiries, and the closer expiry gets, the faster time value decays.

In one line: The expiry date is the day an option contract ceases to exist and is settled — Indian index options have weekly and monthly expiries, and the closer expiry gets, the faster time value decays.

In simple words

Every option has a deadline. On the expiry date, the option is settled: in-the-money options pay out their intrinsic value and out-of-the-money options expire worthless. As expiry approaches, an option loses time value faster and faster. Nifty and Bank Nifty have weekly expiries (every week) and monthly expiries (last week of the month).

Visual

Expiry Date

An at-the-money option's value decays slowly at first and then collapses as the expiry date approaches — the reason expiry timing is so important.

Weekly and monthly expiries in India

The NSE offers weekly expiries for its major index options — Nifty and Bank Nifty settle on specific weekdays each week — plus a monthly expiry that falls in the last week of each month. Weekly options are shorter-dated, cheaper, and decay fast, making them popular for short-term and expiry-day trading. Monthly options have more time value and are used for longer views and positional strategies. (Always check the current NSE calendar, as expiry days and product schedules are revised periodically.)

Why expiry drives time decay

An option's premium includes time value that reflects the chance of a favourable move before expiry. As the expiry date nears, that window shrinks, so time value melts toward zero — this is Theta, and it accelerates. A weekly option can lose a large share of its value in its final two or three sessions. Choosing the right expiry means giving your thesis enough time to play out without paying for time you don't need.

Expiry-day dynamics

On expiry day, options behave dramatically. At-the-money options have enormous Gamma, so their Delta swings violently on small moves, and time value evaporates by the close. This makes expiry day a specialist's game — rich in opportunity for sellers harvesting the final decay, but dangerous for anyone caught on the wrong side of a sharp move with no time left to recover. 'Zero-days-to-expiry' (0DTE) trading has become hugely popular on Indian indices for exactly this volatility.

Settlement at expiry

Indian index options are cash-settled: at expiry, the difference between the settlement price and the strike is credited or debited in cash, with no delivery. Stock options, however, are physically settled — an in-the-money position can result in an obligation to deliver or take delivery of shares, which carries large settlement and margin implications. Traders must close in-the-money stock options before expiry unless they intend physical delivery.

Practical example (Nifty)

Illustrative — Nifty, lot size 75

It is Monday, with a Nifty weekly option expiring Thursday. You buy a 20,000 CE for ₹120. If Nifty stays flat, Theta might erase it to ₹90 by Tuesday, ₹55 by Wednesday and near ₹5–10 by Thursday afternoon — the decay accelerates each day. The same ₹120 of time value in a monthly option, with weeks left, would barely move over those four days. The expiry you choose changes the entire character of the trade.

Why it matters in practice

Weekly options decay fast and suit short-term views; monthly options give more time for positional trades.
Time decay accelerates as expiry nears — a weekly can lose most of its value in the final sessions.
Expiry day has extreme Gamma and vanishing time value — a specialist environment.
Index options are cash-settled; in-the-money stock options can trigger physical delivery obligations.

Common mistakes

Buying weekly options and holding them flat, watching accelerating Theta destroy the premium.
Choosing an expiry too short for the thesis, so the move happens after the option has expired.
Holding in-the-money stock options into expiry and being surprised by physical settlement obligations.
Trading expiry day without respecting the extreme Gamma that turns small moves into large P&L swings.

What professionals do

Professionals match expiry to their time horizon — buying enough time for a thesis to work while avoiding paying for excess. Sellers often favour the back end of the cycle to harvest decay, then step aside from the most Gamma-heavy final sessions unless they are expiry specialists. They track the NSE expiry calendar closely and always close in-the-money stock options before physical settlement forces an unwanted delivery.

Key takeaway

The expiry date is the option's deadline and the engine of time decay. Weekly options decay fast and suit short views; monthlies give room for positional trades. Match expiry to your horizon, respect accelerating Theta, and mind physical settlement on stock options.

Frequently Asked Questions

What is the expiry date of an option?

The expiry date is the day an option contract ends and is settled. In-the-money options pay their intrinsic value; out-of-the-money options expire worthless.

What is the difference between weekly and monthly expiry?

Weekly options expire each week and decay quickly, suiting short-term trades. Monthly options expire in the last week of the month, carry more time value, and suit positional strategies.

Why do options lose value as expiry approaches?

Because time value reflects the chance of a favourable move before expiry, and that window shrinks as expiry nears. This decay, measured by Theta, accelerates in the final days.

What is 0DTE or expiry-day trading?

Zero-days-to-expiry trading means trading options on their expiry day, when time value collapses and Gamma is extreme. It offers opportunity for sellers but is high-risk for buyers caught on the wrong side.

Are Nifty options cash-settled at expiry?

Yes. Nifty and other index options are cash-settled — the profit or loss is settled in cash. Stock options are physically settled and can require share delivery.

What happens if my option is in-the-money at expiry?

For index options it is auto-exercised and cash-settled for its intrinsic value. For stock options, being in-the-money can trigger physical delivery obligations.

Which expiry should I trade?

Match the expiry to your view's time horizon. Short, fast trades suit weeklies; multi-week positional views suit monthlies. Avoid paying for more time than your thesis needs, but don't buy too little.

Why is expiry day so volatile?

At-the-money options have very high Gamma near expiry, so their Delta changes sharply on small moves, while time value disappears by the close — producing large, fast P&L swings.

Can I sell my option before expiry?

Yes. You can close or 'square off' an option any time before expiry by taking the opposite trade, locking in the current profit or loss rather than waiting for settlement.

Sources & references

NSE India — Expiry calendar

Educational content only — not investment advice.