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Why Volatility Changes Near Expiry

Implied volatility behaves differently in an option's final days — it can spike ahead of a known event and then collapse sharply once that event or the expiry itself has passed, even if the underlying barely moves.

Quick answer: Implied volatility behaves differently in an option's final days — it can spike ahead of a known event and then collapse sharply once that event or the expiry itself has passed, even if the underlying barely moves.

In simple words

Implied volatility (IV) is the market's estimate of how much an underlying might move before expiry, expressed as an annualised percentage. As expiry gets closer, there is simply less time left for anything to happen, so IV has less room to price in. If a big event — a Budget, an RBI policy decision, quarterly results — sits just before expiry, IV on the near-dated contract can spike in anticipation and then fall sharply the moment the event passes, a pattern traders call 'IV crush'. This is why an option's price can drop even when the underlying hasn't moved at all.

Purpose

Understanding how IV shifts near expiry stops you from mistaking a fall in option price for a directional loss when it is really a collapse in priced-in uncertainty, and helps you avoid overpaying for options going into a well-known event.

Visual explanation

Why Volatility Changes Near Expiry

As an event or expiry passes, implied volatility often collapses sharply even though the underlying barely moves — the classic IV crush.

eventImplied volatility (%)Time (→ event, then after)

Professional explanation

IV prices uncertainty, and uncertainty shrinks as time runs out

Implied volatility is derived by feeding an option's market price back into a pricing model to solve for the volatility the market is implicitly assuming. It represents expected movement, not decay of time itself — that is theta's job. In the run-up to a scheduled, high-impact event that falls within a contract's remaining life, market participants bid up IV because the range of plausible outcomes widens. Once the event is behind the contract, or once expiry itself closes off any more time for surprises, that priced-in uncertainty has nowhere left to express itself and IV tends to fall back toward a calmer, realised-volatility-anchored level.

The term structure flattens and can invert into a known event

Under normal conditions, further-dated contracts carry slightly higher annualised IV than near-dated ones (a mild contango), because more time means more can happen. But when a specific high-impact event — a Budget day, an RBI policy, a company's results — falls inside the near-dated contract's life and outside the next one, the near-dated IV can spike above the longer-dated IV, a temporary inversion. After the event, the near-dated IV usually falls back below the longer-dated leg, restoring the normal shape of the term structure.

India VIX as a live gauge of this dynamic

India VIX, computed by NSE from the order-book prices of near- and next-month Nifty options, is a forward-looking 30-day volatility measure. It tends to rise ahead of events or turbulent expiry weeks and ease once the relevant options roll off or the event passes, because the underlying option-chain inputs that build the VIX index shift as contracts near expiry and are replaced by the next series. A trader who tracks India VIX around expiry gets an early read on whether the whole option chain — not just one strike — is pricing in elevated uncertainty.

Vega itself shrinks near expiry, compounding the effect

Vega measures how much an option's price changes for a one-point change in IV, and vega mechanically declines as time to expiry falls, because there is less time value left to be sensitive to volatility in the first place. This creates a double effect near expiry: IV itself is prone to sharp swings around events, and the option's sensitivity to that IV move (vega) is simultaneously shrinking. The net result is that IV crush hurts most in the days just before an event, when vega is still meaningful, and matters progressively less in the very last day or two of a contract's life, when gamma and theta take over as the dominant forces.

Practical example (Nifty / Bank Nifty)

Illustrative — Nifty spot 25,000, lot size 75

With Nifty at 25,000 two days before an RBI policy announcement, the weekly 25,000 CE trades with an implied volatility of around 16% versus a calmer 12% the week before, pushing its premium up even though Nifty itself hasn't moved. The morning after the policy decision, with Nifty still near 25,000, IV reverts to roughly 12% and the option's premium falls noticeably — a textbook IV crush that has nothing to do with direction.

India VIX itself often shows this pattern around the Union Budget: it typically ticks up in the days before Budget day as options price in policy uncertainty, then eases once the announcement is made and the near-week options that priced that event roll off toward expiry.

Advantages

  • Predictable event-driven IV patterns let disciplined traders avoid overpaying for options right before a known catalyst.
  • IV crush can benefit option sellers (for example short straddles) when the underlying doesn't move as much as the elevated IV implied.
  • Tracking India VIX gives an early, chain-wide signal of rising or falling expected volatility into an expiry week.

Limitations

  • IV crush magnitude is hard to predict precisely and can be far larger or smaller than expected.
  • A seller positioned for IV crush can still lose heavily if the underlying makes an unexpectedly large move.
  • Buying options right before a known event is structurally expensive, even if the eventual directional call is correct.

Why it matters in practice

  • Avoid buying short-dated options purely for a 'surprise' bet right before a well-known event — elevated IV can erase gains even on the right call.
  • Compare current India VIX to its recent average before sizing an expiry-week trade.
  • Distinguish a price fall caused by IV crush from one caused by a genuine move against your position.
  • Remember vega's influence shrinks fast in the final day or two, when gamma and theta start to dominate instead.

Common mistakes

  • Buying an option right into a known high-IV event and being surprised when the price falls despite being right on direction.
  • Treating every drop in premium as a directional loss instead of checking whether IV has simply reverted.
  • Ignoring the India VIX trend when entering or sizing a position in expiry week.
  • Assuming vega risk stays constant through a contract's life, when it actually shrinks sharply as expiry nears.

Professional usage

Professional volatility traders watch the term structure and India VIX continuously, comparing implied volatility to their own estimate of likely realised movement. They price known events into their entries in advance, size short-volatility positions for the IV crush they expect, and hedge vega exposure ahead of scheduled catalysts rather than being caught by a post-event repricing. For them, IV is a tradable input in its own right, not just a component buried inside the premium.

Key takeaways

  • Implied volatility often spikes before a known event and collapses (IV crush) once it has passed or expiry nears, independent of the underlying's actual move.
  • India VIX is a live, chain-wide gauge of this dynamic around expiry weeks and events.
  • Vega itself shrinks near expiry, so the same IV move matters less in an option's final day or two than earlier in its life.

Frequently asked questions

What is IV crush?
IV crush is a sharp fall in an option's implied volatility — and therefore its price — that typically happens once a known event or expiry has passed, even if the underlying itself hasn't moved much.
Why does implied volatility rise before a big event?
Because the range of plausible outcomes widens when a major catalyst (a Budget, RBI policy, results) is still ahead, so the market prices in more uncertainty by bidding up implied volatility on options covering that period.
Does IV crush mean my option is wrong?
Not necessarily. IV crush is a re-pricing of uncertainty, separate from the underlying's direction — your view can still be correct even as elevated IV reverts and reduces the option's price.
What is India VIX?
India VIX is NSE's index of expected 30-day volatility in the Nifty, computed from the prices of near- and next-month Nifty option contracts. It rises with expected uncertainty and falls as it eases.
Does India VIX rise near expiry?
Not automatically — it tends to rise when a specific event or heightened uncertainty sits within the current expiry cycle, and can stay flat or fall in an uneventful week.
How is implied volatility different from historical volatility?
Historical (realised) volatility measures how much the underlying actually moved in the past; implied volatility is the market's current expectation of future movement, derived from option prices.
Why do option sellers like IV crush?
Because a fall in implied volatility reduces an option's extrinsic value, which benefits a net seller of options, provided the underlying hasn't moved enough to offset that gain.
Can IV crush happen without an event?
Yes. Even without a named event, implied volatility on a near-dated contract can drift lower simply because less time remains for anything unexpected to happen as expiry approaches.
Is vega the same throughout an option's life?
No. Vega is highest when more time remains and shrinks steadily as expiry approaches, so the same change in implied volatility moves the option's price less in its final days than earlier in its life.
Why does the volatility term structure sometimes invert?
It inverts when a near-dated contract's remaining life covers a specific high-impact event that a longer-dated contract also covers but dilutes over more time, pushing the near-dated implied volatility temporarily above the longer-dated one.
Should I buy options right before results or a policy announcement?
Doing so usually means paying an IV-inflated premium that can fall sharply once the event passes, even if you are directionally correct — this is a known risk to weigh, not advice.
How can I tell if a price move was IV crush or a real move?
Compare the option's implied volatility before and after the event alongside the underlying's actual change — if implied volatility fell sharply while the underlying barely moved, IV crush is the likely explanation.
Does IV crush affect both calls and puts?
Yes. Implied volatility crush affects the extrinsic value of both calls and puts at a given strike and expiry roughly symmetrically, since it reflects overall expected movement, not direction.
Is implied volatility the same for every strike?
No. Different strikes on the same expiry typically show different implied volatilities — a pattern known as the volatility skew — even though they all react to the same underlying event.

Voice search & related questions

Natural-language questions people ask about Why Volatility Changes Near Expiry.

Why did my option lose value even though Nifty didn't move?
Most likely implied volatility fell — a fall in priced-in uncertainty (IV crush) reduces an option's premium independent of the underlying's actual move.
What is India VIX and why does it matter for expiry?
It's NSE's gauge of expected 30-day volatility in Nifty, built from option prices; it often rises before big events and eases once they pass, giving a quick read on market nervousness into expiry.
Is it a bad idea to buy options right before the Budget?
It can be expensive, because implied volatility is usually elevated going in and can crush lower right after the announcement, even if your direction call is right.
Why do option prices fall right after big news?
Because the uncertainty that news was supposed to resolve is now gone, so implied volatility — and the extra premium it added — often collapses quickly.
Does implied volatility matter more early or late in an option's life?
Early — vega (sensitivity to implied volatility) is highest when more time remains and shrinks sharply as expiry approaches.

Sources & references

Last reviewed 11 July 2026. Educational content only — not investment advice. Exchange rules change; verify current conventions on NSE/BSE.

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