Introductory Context
"IV crush occurs when the implied volatility that inflated an option's premium collapses after an event resolves — even if the direction was correct. The vega loss from IV falling can exceed the delta gain from the directional move. IV crush is most severe when options are bought at peak pre-event IV. Spread structures and pre-event timing are the primary defences. "
The Mechanism — How IV Crush Works
Every options premium has two components: intrinsic value and time value. Time value is heavily influenced by implied volatility — specifically through vega. Before a major event (Budget, RBI, election), IV rises as uncertainty increases. The time value component of options premiums swells. Then the event is announced. Uncertainty resolves. The demand for options protection collapses. IV falls rapidly — often 30–50% within hours. The time value component of premiums falls proportionally. If you are holding a long option during this collapse, your position loses the vega-driven time value even while it may be gaining intrinsic value from a directional move.
The IV crush loss: vega × change in IV. If your option has vega of ₹6 per unit and IV falls 6 percentage points (say from 20% to 14%), your option loses ₹6 × 6 = ₹36 per unit purely from the IV collapse — before any directional gain or loss is counted. Against this ₹36 vega loss, your directional gain of delta × Nifty move must exceed for a net profit.
The Budget Example That Shows the Trap
Priya bought a Nifty 24,200 CE for ₹160 on January 31 (Budget day) when VIX was at 22. The Budget was announced. Nifty rallied 350 points. Priya checked her position. Delta gain: 0.50 × 350 = ₹175 per unit. Vega loss: ₹8 × (22 − 11) = ₹8 × 11 = ₹88 per unit. Net P&L: ₹175 − ₹88 = ₹87 per unit gain — better than breakeven, but far less than the ₹175 pure directional gain would suggest. Now imagine if Nifty had rallied only 150 points: delta gain ₹75, vega loss ₹88, net P&L: −₹13 per unit loss. Correct direction. Wrong about the magnitude. Loss caused by IV crush.
Calculating the IV Crush Impact
Before buying an option ahead of any event where IV crush is expected, calculate the impact:
• Step 1: Identify current IV (from option chain or India VIX)
• Step 2: Estimate post-event IV (typically 55–65% of pre-event IV for Budget/RBI)
• Step 3: Calculate IV change = current IV − expected post-event IV
• Step 4: Find the option's vega (from Sensibull or broker platform)
• Step 5: Vega loss per unit = vega × IV change (in percentage points)
• Step 6: Required directional gain to overcome vega loss = vega loss ÷ delta
Example: Pre-Budget Nifty ATM call, current IV 20%, expected post-Budget IV 12%, vega ₹7/unit, delta 0.50. Vega loss = ₹7 × 8 = ₹56/unit. Required Nifty move to break even: ₹56 ÷ 0.50 = 112 points — just to overcome the IV crush. Any Nifty rally below 112 points produces a net loss despite a positive directional outcome.
The Three Defences Against IV Crush
Defence 1 — Timing: Enter Before Peak IV
Enter positions 7–14 days before the event rather than on the event day. At this stage, IV has begun rising but is not yet at peak. You capture the remaining pre-event IV expansion (vega gain) rather than facing post-event IV collapse. By exiting 1–2 days before the event, you capture the optimal risk-reward without holding through the IV crush.
Defence 2 — Structure: Use Spreads to Reduce Net Vega
A Bull Call Spread (buy ATM call, sell OTM call) reduces net vega exposure. The OTM call you sell has its own vega — when IV collapses, this short vega position gains, partially offsetting the long call's vega loss. The spread does not eliminate IV crush — but it significantly reduces its impact compared to a naked long call.
Defence 3 — Sizing: Reduce Position Size in High-IV Environments
Accepting that some IV crush is likely and trading smaller accounts for it. Instead of the standard position size for VIX 14, use half or one-third the standard size when VIX is at 20+. The directional gain potential is proportionally reduced but so is the IV crush loss impact.
The Best Approach — Combine All Three
Optimal event strategy: enter 10 days before (timing), use a spread structure (structure), and size at 70% of standard (size). This triple-defence approach captures the event's directional potential while managing IV crush to a manageable impact. It produces lower maximum gains than a naked long at peak IV — but dramatically better expected value across the realistic range of event outcomes.