Concept
Expiry Day Mechanics
Expiry is the last day a derivative contract exists. Positions still open at the close are settled against a final settlement price rather than at the last traded price, and the contract ceases to exist.
How to read it
- The final settlement price for index contracts is derived from a volume-weighted average of the underlying over a defined closing window, not from the last traded price of the contract itself.
- Any position still open at expiry is settled automatically. There is no option to carry it — the contract stops existing.
- Options finishing in the money are exercised; options finishing out of the money expire with no value.
Why the settled price can differ from the last traded price
Suppose an index future is trading at 22,480 in the final minutes. The final settlement price is computed from a weighted average of the underlying index over the closing window, and that average works out to 22,455. Positions settle against 22,455, not 22,480. On a single lot the 25-point difference is real money, and nothing about the contract price in those last minutes changed the outcome. This is ordinary mechanics rather than an error, and it is one reason expiry-day behaviour is worth understanding before holding a position into it.
What it does not tell you
- The settlement price is calculated from the underlying, so a derivative can trade at a level meaningfully away from where it eventually settles.
- Conditions on expiry day are frequently different from other days: premiums decay fast, spreads can widen, and liquidity concentrates in particular strikes.
- Exact windows and procedures are set by the exchange and change from time to time. Verify current rules with NSE rather than relying on any summary, including this one.
Frequently asked questions
What happens if I do not square off before expiry?
The position is settled automatically against the final settlement price. Index derivatives settle in cash; stock derivatives in India settle by physical delivery, which has significantly different consequences.
How is the final settlement price determined?
For index contracts it is based on a volume-weighted average of the underlying index over a defined closing window on expiry day, not on the last traded price of the derivative.
Why is expiry day different from other days?
Remaining time value collapses toward zero, so premiums move differently. Spreads can widen and activity concentrates in strikes near the settlement level.
Can I roll a position instead of letting it expire?
Closing a position in the expiring contract and opening one in a later contract is possible and commonly called rolling. It is two separate transactions with their own costs, not a single continuous position.
Related
- Physical vs Cash Settlement — Concept
- STT on Expiry: Why the Charge Can Be Larger Than Expected — Concept
- Theta (Time Decay) — Concept
Educational use only
This page is educational material about how a technical tool is calculated and read. It is not investment advice, not a recommendation to buy or sell anything, and not a signal service. No indicator predicts future prices. CernoQuant is a trading journal and analytics platform, not a SEBI-registered investment adviser. Trading decisions and their outcomes are yours alone.
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