Option selling margin: why it is so much higher

Why is option selling margin so much higher than buying? It's based on the index's notional value, not the premium. Here's a worked Nifty example.

12 August 2026 7 min read #margin #options #risk

Option selling margin is much higher than buying because the seller's loss has no fixed limit, so margin is set as a percentage of the underlying's full value, not the premium. A buyer can only lose what they paid. A seller has to put up enough to cover a bad day in the index.

Here's how big the gap is. Buy one lot of a ₹40 Nifty option and it costs you ₹40 × 75 = ₹3,000. Sell the same contract and your broker blocks something like ₹2,00,000 or more. Same strike, same expiry, around seventy times the money.

New traders often think the broker is being difficult. It isn't. Once you see why, you can size a short option properly instead of blowing up your account on a trade that "only" collected ₹3,000.

Why is the margin for buying and selling options different?

When you buy an option, you're buying a right. The most you can lose is what you paid. If the trade goes fully against you, the option expires worthless and you're out ₹3,000. Your loss has a floor, and you've already paid it. There's nothing more to cover, so the margin is just the premium.

When you sell an option, you're taking on an obligation. You get ₹3,000 today. In return you've promised to pay a difference that's only limited by how far the index moves. If Nifty gaps 500 points against a short call with 75 units per lot, you're looking at around ₹37,500 on one lot. That's about twelve times the premium you collected.

Nobody knows the worst case in advance. So the system asks a different question: how much money would cover a bad but realistic day? The answer has nothing to do with the premium.

How is option selling margin calculated?

The main idea is simple:

Short-option margin is a percentage of the notional value of the underlying, not a percentage of the premium you received.

Notional value means the full value of what the contract controls, which is the index level × lot size.

Take Nifty at 24,500 with a lot size of 75.

Item	Amount
Notional value of one lot (24,500 × 75)	₹18,37,500
Margin at an assumed 12%	₹2,20,500
Premium collected (₹40 × 75)	₹3,000

In real life the exchange's margin is made of SPAN margin plus exposure margin, and together they usually land somewhere around 10–15% of notional. We've used 12% to keep the maths simple.

So the premium is ₹3,000 and the margin is ₹2,20,500, roughly seventy-three times more. Nobody is punishing you. ₹3,000 just isn't enough collateral for a promise on ₹18 lakh worth of index.

Why does a cheap OTM option need almost the same margin?

This confuses people even more. A far out-of-the-money (OTM) short option needs nearly as much margin as an at-the-money one.

A ₹2 option and a ₹200 option on the same index and expiry have margins fairly close to each other. The margin comes from the notional value, which they share. The premium, which differs a hundred times, barely matters to it.

So selling a cheap option isn't a small position. It's the same size of position with a smaller reward.

What return do you really make selling options?

Once you treat the margin as the money you've actually committed, option selling looks different from how it's usually sold to beginners.

Using the numbers above, you collect ₹3,000 and block ₹2,20,500. If the option expires worthless and you keep all of it, that's a 1.36% return on the capital you tied up, before charges. And charges will take a visible bite. There's at least ₹40 of brokerage for the round trip, plus STT on the sell leg, exchange fees and GST.

Put plainly, a naked short option (one with no protective leg) ties up a lot of capital to earn a small percentage most of the time. Once in a while it loses many times what it usually makes. That can be a fine business, but it's a different business from "I collected ₹3,000 on ₹3,000 of margin". A poorly built simulator will show you that second picture.

It's also why the usual reward-to-risk thinking from option buying doesn't work here. Your risk isn't the premium. It's the position size the margin is pointing to.

Why do spreads need less margin?

Sell a call and at the same time buy a call further out of the money. The margin drops a lot, often to a small part of what the naked short needed.

The reason is the same idea, just turned around. With the bought call in place, your loss is no longer open-ended. Above the higher strike, the two legs cancel each other out. Your maximum loss is a known number:

(difference between strikes − net premium received) × lot size

Once the worst case has a clear limit, the margin only has to cover that limit.

So the case for spreads is mechanical: a limited worst case needs less collateral than an unlimited one, and the capital you free up is real.

How much of your account should you use for option selling?

Size on margin, not on premium. Before you sell, check what part of your account the margin uses. Two lots of a short Nifty option at about ₹2.2 lakh each is ₹4.4 lakh of margin. On a ₹5 lakh account, that's 88% of your money on one view. The fact that you collected only ₹6,000 doesn't change that.

Lower intraday margin doesn't mean lower risk. Brokers often offer reduced intraday margin on F&O. That's a funding relief, not smaller exposure. If the market gaps, your obligation is exactly the same, you just have less money behind it. A short on intraday margin is more dangerous than a fully margined one.

No underlying price means no margin number. To work out short-option margin you need the underlying's current price, since the notional is built from it. Without that price you can't calculate margin. The right move then is to refuse the order, not guess using some multiple of the premium. A simulator that guesses would let you take a position you could never hold in a real account. This app refuses the order instead, for exactly that reason.

What margin rules don't protect you from

Margin limits how much notional you can control. It says nothing about whether putting that much on one idea is sensible.

A trader who sells the maximum lots their account allows, on one strike, in one expiry, has followed every margin rule. They've also taken a very concentrated bet.

If it works, the equity curve goes up smoothly. No drawdown, no red days, a great return. Every risk number worked out from the result looks excellent, because those numbers measure the risk that happened, not the risk that was taken.

That's why "how much of the account went into one position" should be tracked as its own number, apart from drawdown and return. Margin is a solvency rule set by someone else. Deciding position size and judging risk is still your job.

Quick answers

Why is option selling margin so high?

A seller's loss isn't capped, so margin is based on the underlying's notional value (index level × lot size), not the small premium. With Nifty at 24,500 and a lot of 75, 12% of notional is about ₹2,20,500.

How much margin do you need to sell one Nifty option lot?

It depends on current SPAN and exposure margins, usually around 10–15% of notional. In our example that's roughly ₹1.8 lakh to ₹2.8 lakh per lot. Check your broker's margin calculator for the live number.

Do far OTM options need less margin to sell?

Only a little less. Margin is driven by the notional value, which is the same for every strike on that index and expiry, so a ₹2 option and a ₹200 option need margins fairly close to each other.

Why does a spread reduce margin?

Buying a further OTM option caps your maximum loss at a known amount. Since the worst case is limited, the margin only needs to cover that amount.

These figures are illustrative. Lot sizes, SPAN percentages and exposure margins change, and your broker's number will differ, so check your own margin statement. This isn't investment advice.

Try it on a simulator first.

₹1,00,000, real NSE prices, and every charge in this post applied to every trade.

Start with ₹1,00,000