Monthly Expiry

Quick answer: Monthly Expiry refers to index and stock option and futures contracts that expire at month-end, carrying more total time value, slower per-day decay, deeper far-strike liquidity, and the rollover flows on which positional structures and calendars are built.

In simple words

A monthly option is a contract that lives until the end of the expiry month. Because it has more time, it costs more than a weekly, its value melts more slowly day by day, and it reacts more calmly to small moves. Traders holding a view that needs weeks tend to use monthlies, and structures that need two different expiries, like calendars, are built around them. As one month ends, positions are often moved to the next month — this is called rollover. NSE sets the expiry day and revises it, so the current specification should be checked on the exchange website.

The two forces at expiry

Professional explanation

The last-Thursday convention, set and revised by NSE

Index and stock derivatives have conventionally expired on the last Thursday of the contract month, moving to the previous trading day when that Thursday is a holiday. That convention is set by the exchange and has been revised — expiry weekdays for various instruments have changed, and readers should confirm the current expiry day for each product on the NSE website. What matters conceptually is that the monthly is the anchor contract of the cycle: the deepest, widest series against which weeklies and calendars are referenced. The specific weekday is an administrative detail the exchange controls, not a permanent fact.

More premium and slower decay than a weekly

A monthly holds thirty-odd days of extrinsic value, so in rupees it is far dearer than a weekly, and its per-day theta is correspondingly gentler. Because at-the-money theta scales as 1/√T, a thirty-day option loses value at roughly one-fifth the per-day pace of a one-day option. On the schematic, the monthly begins its life in the shallow left region of both the theta and gamma curves and only enters the steep zone in its final week. That extra time is what lets a directional or positional view breathe.

Deeper liquidity in the far strikes

While the nearest weekly concentrates volume at the money, the monthly carries usable liquidity across a much wider range of strikes, including deep out-of-the-money wings. Positional traders, hedgers and structure-builders need those far strikes to be tradable, and the monthly is where they are. This is why four-leg structures, protective wings and ratio positions intended to be held are usually built on the monthly rather than the weekly, whose wings can be thin and whose gamma is punishing.

The contract that calendars and positional structures are built on

A calendar or diagonal spread sells a near expiry against a far one and lives on the difference in their decay rates. That difference exists precisely because theta scales as 1/√T — the near leg decays faster than the far leg. The monthly, and the contract beyond it, supply the far leg. Any structure that depends on time, on a slower-decaying long, or on holding through an event, is anchored to the monthly. The weekly is a tool for the last few days; the monthly is the tool for the weeks before them.

Construction

1. Read the two panels for the same at-the-money option: theta and gamma against days to expiry.
2. Locate where a monthly spends its life — the shallow left region of both curves for most of its term.
3. See that only in the final week does a monthly enter the steep zone the weekly lives in permanently.
4. For rollover, compare the price of the expiring contract with the next month's, and check current expiry dates on the NSE website.

Market outlook

A trader may study monthly contracts when a view needs weeks to play out, when a structure requires two expiries, or when far-strike liquidity matters — a protective wing, a calendar's long leg, a positional hedge. The condition that invalidates the monthly's appeal is a purely short-horizon idea, where the extra premium paid for time is wasted and a weekly would express the view more cheaply. As with any expiry, the contract itself is direction-agnostic; the outlook lives in how it is used, not in the tenor.

Risk profile

As with the weekly, risk depends on use, and this page is marked defined only for the narrow case of a monthly option bought outright, whose loss is capped at the premium paid. A short monthly position carries undefined risk, though its gamma is far gentler than a weekly's until the final week, which is why positional short-premium structures prefer the monthly's early life. The defining safety of the monthly relative to the weekly is time: more days means lower gamma and a cushion of extrinsic value that absorbs moves a weekly would convert straight into intrinsic loss.

Reward profile

For a buyer, the monthly's reward is durability — a directional view has weeks to be right, and the position does not bleed as fast as a weekly. For a seller, the reward is a larger absolute credit spread over a longer, gentler decay, with far-strike liquidity to build defined-risk wings. In both cases the trade-off is the mirror of the weekly's: more time means more premium at stake and slower decay, so patience is required and gamma only becomes dangerous in the last week.

Margin requirement

A long monthly costs its premium. A short monthly attracts SPAN plus exposure margin; because early-life gamma is lower than a weekly's, intraday margin is steadier until the final week, when it can rise as gamma climbs. NSE and brokers revise margin rules and can raise them near expiry. Rollover involves margin on both legs briefly if the old and new contracts overlap. Confirm current margin policy with the broker and exchange.

Greeks exposure

Volatility impact

For most of its life a monthly has real vega, so a rise in implied volatility lifts its price meaningfully — helping a holder, hurting a short — and a fall does the reverse. This is why known events sitting inside the contract month matter: implied volatility can inflate ahead of an event and crush after it, moving a monthly's price even if the index does not travel. As the monthly enters its final week, vega collapses and the contract behaves more like a weekly, becoming insensitive to IV and increasingly driven by intrinsic value and gamma.

Time decay

A monthly spends most of its term in the shallow part of the decay curve, losing value slowly, and only accelerates in the last week. Because at-the-money theta scales as 1/√T, the thirty-day option's per-day decay is roughly one-fifth of the one-day option's. This gentle early decay is exactly what calendars monetise: sell the fast-decaying near contract against the slow-decaying far one. On the schematic, the monthly is the left half of the theta curve — flat and forgiving — until the final days pull it into the steep zone the weekly occupies from birth.

Practical examples

Lot sizes used above (NIFTY 75, BANKNIFTY 30) are those in force at the time of writing; NSE revises them periodically. Figures exclude brokerage, STT, exchange charges, stamp duty and GST, all of which materially affect small spreads.

Common mistakes

• Paying for a monthly's time value to express a view that will resolve in two days, wasting the extra premium a weekly would not have charged.
• Reading rollover data as a forecast: the roll spread and rollover percentage describe how positions are being moved, not where the index will go, and treating them as predictive invites disappointment.
• Forgetting that a monthly turns into a weekly in its final week — gamma and theta both steepen, so a position that behaved calmly for three weeks can lurch in the last five days.
• Assuming the last-Thursday convention is permanent: NSE has revised expiry weekdays for various instruments, and a calendar or roll timed to an old date can be mistimed.
• Selling a monthly for its larger credit without respecting that the loss is still uncapped in the tails; the gentler gamma reduces the odds of ruin, it does not remove them.
• Rolling a losing position to the next month reflexively to avoid booking a loss, which converts a defined outcome into a larger open-ended one and pays a fresh spread to do so.

Advantages & disadvantages

Professional usage

Desks and institutions use monthlies as the backbone of positional and volatility books: calendars and diagonals sell near expiries against far ones, hedges are placed in liquid far strikes, and rollover is managed as a scheduled, cost-controlled operation rather than a reflex. They read rollover flows as a descriptive census of positioning across the market, never as a directional signal, and they cross-margin the roll so the brief overlap of two contracts costs little. A retail trader can trade the same monthlies but without the cross-margin, the continuous hedging or the flow data, so the roll is a discrete cost and the structures carry their raw Greeks.

Frequently asked questions

Voice search & related questions

Natural-language questions people ask about the Monthly Expiry.

Sources & references

• NSE — contract specifications, expiry and settlement
• SEBI — regulations and derivatives market studies
• Hull, Options, Futures, and Other Derivatives

Last reviewed 9 July 2026. Educational content only — not investment advice.