What is expiry day in F&O trading?

Every derivative contract has a fixed expiry. Until that day it can be bought and sold freely; on expiry it is settled and removed from the market. For options, settlement compares each strike with the closing settlement price of the underlying: in-the-money options carry value and are settled accordingly, while out-of-the-money options expire worthless and the buyer loses the entire premium.

On NSE, index options such as Nifty and Bank Nifty are cash-settled, so no shares change hands — the difference is simply credited or debited. Stock options that finish in the money can involve physical delivery, meaning actual shares must be given or taken. A trader holding such a contract into expiry needs to understand that obligation in advance.

NSE offers weekly expiries for the headline index options and monthly expiries across instruments. Monthly contracts expire on a scheduled day each month, while weekly contracts give shorter-dated options that expire every week. The exchange sets and occasionally revises the expiry schedule, so traders confirm the current calendar rather than assume a fixed weekday.

Shorter-dated contracts behave very differently. A weekly option has little time left, so its time value decays rapidly and its price can swing violently on small moves in the underlying. This is why expiry-week and especially expiry-day options attract speculation — and why they are so hazardous for those who do not understand the decay working against them.

As expiry approaches, the time value in an option collapses toward zero — an effect that is fastest on the final day. An at-the-money option can lose much of its value within hours simply because time is running out, even if the underlying barely moves. Buyers feel this decay acutely, while sellers benefit from it if the underlying stays put.

Expiry sessions also see large positions being closed, rolled or settled, which can concentrate activity around heavily traded strikes. The result is often rapid, whippy price action where an option doubles or halves quickly. These moves look like opportunity but are driven by mechanics that punish poor timing and undefined risk.

Traders who want to keep a position beyond expiry do not simply let it lapse — they roll over, closing the expiring contract and opening the equivalent in the next expiry. This is common in futures and in longer-horizon options strategies, and it carries its own cost from the spread between the two contracts.

Letting a position expire by accident can be costly, particularly in stock options where physical delivery may be triggered. Knowing whether you intend to settle, square off before the close, or roll over is part of managing an F&O position, a topic covered further in our rollover and futures-versus-options guides.

Buying very cheap, far-out-of-the-money options on expiry day in the hope of a quick multiple is one of the most common ways new traders lose money. The premiums are low because the probability is low; the overwhelming majority of such options expire worthless. The low cost is the warning, not the attraction.

This sits inside a sobering picture. SEBI's study released in September 2024 found that roughly 93% of individual F&O traders lost money in FY24, with aggregate losses exceeding 1.8 lakh crore rupees across FY22 to FY24. Expiry day concentrates the very forces — leverage, time decay and volatility — that drive those losses. It rewards a disciplined, tested process and defined risk, never speculation dressed up as opportunity.