Exposure Margin
SPAN guesses the worst likely day. Exposure margin is what the exchange keeps in case the guess is wrong.
In short: exposure margin is a flat percentage of contract value collected in addition to the SPAN margin on every futures and short-option position on NSE. It does not depend on scenarios or volatility; it is there to cover losses beyond what the SPAN risk arrays anticipate. Together, SPAN plus exposure is the initial margin that must be in the account before the trade.
The intuition
The SPAN margin is a model. It takes the exchange’s volatility estimate, imagines a set of price and volatility moves, and charges the worst loss among them. Models fail on exactly the days that matter: a gap on a policy announcement, a global shock overnight, a circuit-limit day. Rather than pretend the model is complete, the clearing corporation adds a second layer that ignores the model entirely and charges a simple percentage of what the position is worth. That layer is the exposure margin; the term extreme loss margin is used for the equivalent charge in the cash segment and for the additional charge on short index options on expiry day.
Because it is a flat rate, exposure margin does not fall when volatility is low. It is the floor under the margin requirement in quiet markets, and it is the part of the requirement a trader can forecast exactly from the contract value.
Formula
Exposure margin = exposure rate × underlying price × lot size × number of lots
For a written option the contract value used is the underlying’s notional, not the premium: a short Nifty option with a ₹50 premium still carries exposure margin on the full 24,000 × 65 notional. For a long option there is no exposure margin, because there is no obligation beyond the premium paid.
Worked example (illustrative numbers)
Suppose NIFTY is at 24,000 and a trader writes one lot (65 units) of a 23,700 put for ₹120, receiving ₹7,800. With an illustrative exposure rate of 2% on the ₹15,60,000 notional, the exposure margin is ₹31,200. If the SPAN component for this put is ₹95,000, the total blocked is ₹1,26,200 less the ₹7,800 premium credit, about ₹1,18,400.
| Scenario | SPAN | Exposure | Total |
|---|---|---|---|
| Calm market, IV 11% | ₹80,000 | ₹31,200 | ₹1,11,200 |
| Normal market, IV 14% | ₹95,000 | ₹31,200 | ₹1,26,200 |
| Stressed market, IV 22% | ₹1,45,000 | ₹31,200 | ₹1,76,200 |
The exposure line is constant across the rows while the SPAN line nearly doubles. In a calm market exposure margin is a quarter of the total; in a stressed one it is under a fifth. That is the design: a floor that matters most when the model is relaxed.
Why it matters to an options trader
- It is the predictable part of a writer’s capital. Contract value times the rate; it can be budgeted before the SPAN file is known.
- It makes far-OTM writing less free than it looks. A ₹10 option carries the same exposure margin as a ₹400 one, so the return on margin for deep-OTM writes is thin.
- It is not reduced by spreads the way SPAN is. Exchanges give some exposure relief on fully hedged spreads, but the SPAN saving is the larger part of why a spread needs less capital.
- Expiry-day short index options carry an extra charge. The 2% extreme loss margin added from November 2024 is of the same kind: a flat cushion against gamma risk the scenarios may understate.
Common mistakes
- Reading the SPAN line alone. Calculators show two lines; the trade needs both.
- Computing it on premium. Exposure margin is on the underlying notional, which for a Nifty lot is ₹15 lakh or more.
- Expecting it to fall in quiet markets. It is a rate on notional; only a lower index or a circular changes it.
- Forgetting stock-specific rates. Stock futures use a higher rate than index futures, and volatile stocks carry additional margins published by circular.
Indian-market specifics
- SEBI set the exposure margin for stock futures at the higher of 5% or 1.5 standard deviations of daily logarithmic returns of the stock over the previous six months, revised down from 10% (SEBI circular on exposure margin for exchange-traded equity derivatives, 2010). Index futures and options carry a lower fixed rate published in exchange circulars.
- Exposure margin is collected upfront together with SPAN under SEBI’s peak-margin framework (fully effective 1 September 2021); a shortfall attracts penalties on the broker, which are passed to the client.
- A 2% extreme loss margin applies to short index options on their expiry day on NSE from 20 November 2024, under SEBI’s index-derivatives framework of October 2024.
- Exchanges impose additional or ad hoc margins on specific stocks when concentration or volatility is high; these appear as a separate line in the broker’s calculator and are also flat percentages of notional.
FAQ
What is the difference between SPAN margin and exposure margin?
SPAN is model-based and variable; exposure is a flat percentage on top.
How much is the exposure margin on Nifty futures?
Each 1% of rate on a 24,000 Nifty lot is ₹15,600; see the live rate.
Is exposure margin charged on option buyers?
No; it applies to futures and short options only.
Is exposure margin the same as extreme loss margin?
Same purpose; different names in different segments.
Estimate both margin lines before you write
The SPAN and exposure margin calculator shows the risk component, the exposure component and the premium credit for a futures or short-option position. In the app, the Option Chain page carries the implied volatility that moves the SPAN line.
Related terms
- Initial Margin, SPAN plus exposure
- SPAN Margin, the scenario-based component
- Peak Margin, the upfront-collection rule
- Notional Value, what the rate is applied to