Stock Futures Explained: Lot Size, Margin & F&O Ban

You thought you were simply buying one familiar stock. By evening, a broker message says your margin is short and the position is about to be cut.

That is the side of single-stock futures nobody mentions when they call it "just leverage on a share you already know."

Single-stock futures are where most retail derivatives accidents in India quietly happen. Not in options, not in index futures, but in the SBI and Reliance lots that beginners pick up because they already follow the underlying stock.

The product looks like a leveraged version of the cash share you already own. It is not.

This article walks through what a stock future actually is, the five pieces that change versus an index future, a worked Reliance trade in rupees, when the product fits and the F&O ban list that beginners often discover the hard way.

What stock futures actually are

A stock future is the single-name version of a futures contract. Instead of locking in a price on Nifty or Bank Nifty, you lock in a price on Reliance, SBI, TCS or any of the more than two hundred individual securities that the NSE has admitted into its F&O segment. That list is set by SEBI's eligibility rules and reviewed periodically, so the exact count drifts over time.

The economics are the same as any other future. You agree today to buy or sell a fixed quantity of shares at a specific price on a specific future date. The money you put down upfront is only the margin, not the full contract value.

Three things change once the underlying goes from an index to a single stock.

The margin requirement is higher, because a single name swings more than a fifty-stock basket. The expiry calendar shrinks to monthly only, with no weekly variant. And from the October 2019 expiry onward, the contract is settled by physical delivery of the shares at expiry, not by cash.

That last piece is the one most beginners miss. Hold a Reliance future to the last Tuesday and you will be obliged to take delivery of 500 actual Reliance shares, with the full contract value debited from your account that evening.

The F&O ban list is the second piece beginners discover unpleasantly. When too much open interest builds up on a single stock, the NSE freezes fresh positions on that name for everyone, sometimes for days at a time. No similar mechanism exists on Nifty or Bank Nifty.

Five pieces of a stock future

Every stock future has the same five pieces as an index future, with stock-specific values for each. Once these are clear, every stock future on every NSE underlying works the same way.

First, the underlying. This is the specific company whose shares the contract is based on. Reliance, HDFC Bank, SBI, ICICI Bank, TCS and Infosys are the most actively traded names by volume.

Out of the 200-plus stocks in the F&O segment, only a much smaller subset — a few dozen of the most active names — see meaningful daily volume. The rest trade thinly enough that the bid-ask spread — the gap between the best buy price and the best sell price, a hidden cost on every trade — eats into a small trader's edge.

Second, the lot size — the fixed number of shares in one contract. You cannot buy half a lot. The NSE fixes the lot for each stock so that one contract is usually worth several lakh rupees; the rule is that the contract value should not be less than ₹5 lakh when the contract is first introduced.

Reliance, for instance, trades in lots of 500 shares — revised up from 250 after its 1:1 bonus issue in late 2024. Every stock has a different lot, and the exchange revises it from time to time after a bonus, a split or a big price move. Always check the current lot in the NSE contract file before you trade; never assume last year's number.

Third, the expiry. Single-stock futures expire on the last Tuesday of the expiry month. If that Tuesday is a trading holiday, the contract expires on the previous trading day. Unlike the Nifty index, there is no weekly variant.

The expiry day used to be the last Thursday — the NSE moved it to Tuesday from September 2025, so any older note you read may still say Thursday. Get this one right; it is the day delivery is forced on you.

At any time, three monthly stock-future contracts trade in parallel for each underlying — a three-month trading cycle. The near month, the next month and the far month all quote prices, and almost all retail volume sits in the near-month contract.

Fourth, the margin. Stock futures need roughly fifteen to twenty-five per cent of the contract value as initial margin for liquid names, collected upfront. It is charged as SPAN plus an extreme-loss margin set by the exchange, it changes daily with the stock's volatility, and it runs higher for more volatile names.

A Reliance lot of 500 shares around ₹1,350 has a contract value of roughly ₹6.8 lakh, so the margin works out to about ₹1.3 to ₹1.5 lakh per lot. A more volatile name like Adani Enterprises can demand close to thirty per cent of contract value.

Fifth, physical settlement — taking or giving the actual shares at expiry, instead of just settling the profit or loss in cash. Since the October 2019 expiry, every stock future that is not closed before expiry settles this way.

A long Reliance future taken to expiry obliges you to pay the full contract value, about ₹6.8 lakh, and receive 500 Reliance shares in your demat. A short Reliance future obliges you to deliver 500 shares to the buyer. Exchanges also levy extra delivery margins in the last few days before expiry on positions likely to go to delivery, so the cash squeeze starts before the final day. Most retail traders close the position well before the last Tuesday to avoid the whole obligation.

A worked Reliance stock-futures trade

These are illustrative numbers around late-May 2026 prices — use them to follow the mechanics, not as today's quote. Reliance is sitting at about ₹1,350 on the spot market. The current-month Reliance future is quoting around ₹1,360. That small premium is the cost of carry — the small gap between futures and spot price, tied to interest and the time left to expiry — not the market shouting that Reliance is going up.

You buy one lot. The lot size is 500 shares, so your contract value is 500 × ₹1,360 = ₹6,80,000.

The NSE collects about twenty per cent initial margin on Reliance, and the broker adds a small buffer on top. In practice you need roughly ₹1,35,000 in your account to take this single trade.

For ₹1.35 lakh, you control ₹6.8 lakh of Reliance exposure. That is about five times leverage — controlling a large position with a small amount of money, which magnifies profit and loss alike.

Suppose Reliance climbs to ₹1,390 over the next two sessions. The future moves with it to roughly ₹1,400. Your profit is (₹1,400 minus ₹1,360) × 500 = ₹20,000 on a margin of ₹1.35 lakh.

That is roughly fifteen per cent return in two days. The leverage made a three per cent move on the share look like fifteen per cent on your money.

Now run the same trade in reverse. Suppose Reliance fell to ₹1,305 after a weak quarterly result, and the future drifted to around ₹1,315. Your loss is (₹1,360 minus ₹1,315) × 500 = ₹22,500.

That loss is not patiently waiting until expiry. The mark-to-market debit — the daily settlement of your running profit or loss into your account — hits you on each of those evenings. If your margin balance drops below the maintenance level, the broker either asks for fresh funds or closes the position out at a loss.

Read that bar carefully. The same three per cent move that looks unremarkable on the share becomes fifteen per cent on your account. That works beautifully when you are right.

It works equally brutally when you are wrong. Most beginners size their stock-futures positions as if the leverage does not exist, then are shocked when a single weak Q4 result erases a quarter of their account.

Stock futures vs cash equity vs index futures

The same Reliance trade can be expressed three different ways. Each route has a completely different risk and capital profile.

In the cash market, you buy 500 Reliance shares at ₹1,350. You pay the full ₹6.8 lakh upfront, you own the shares, there is no expiry and the worst case is the company going to zero. You also collect any dividends declared during your holding period.

In the stock-futures market, you buy one Reliance future lot. You pay roughly ₹1.35 lakh of margin, you control the same ₹6.8 lakh of exposure, the position expires on the last Tuesday, and mark-to-market settles your profit or loss every evening. You do not collect the dividend — the futures price already adjusts for it through the cost of carry.

In the index-futures market, you take a single Nifty lot. The lot value runs to ₹15 lakh or more — index derivatives now carry a higher minimum contract value than single stocks — the margin is a smaller share of that value, and the exposure is to fifty stocks instead of one. You give up Reliance-specific upside in exchange for a smoother ride.

Beginners look at the second box and see the five-times figure as opportunity. Experienced traders look at the same box and see five-times responsibility.

The contract you are signing is the same in both cases. What changes is how the trader thinks about position size, stop placement and the maximum loss they are willing to wear before the position is even entered.

Where stock-futures traders blow up

SEBI's study released in September 2024 found that 93% of individual equity F&O traders lost money, net of costs, across the three years from FY22 to FY24.

That figure covers the whole futures-and-options segment, which is dominated by options, not single-stock futures — so stock futures are not what drives the headline. But they carry the very same trap that sinks most retail traders: leverage used without discipline. Options simply get more of the attention.

The first place beginners blow up is the F&O ban list. A stock enters ban when its open interest crosses ninety-five per cent of the market-wide position limit (MWPL) — the largest combined derivatives position the whole market is allowed to hold in that one stock.

While the stock is in ban, no fresh positions are allowed. Existing positions can be closed, but anyone caught taking a new position pays a stiff exchange penalty plus their broker's own surcharge. Beginners frequently get caught here on volatile names like RBL Bank, BHEL, Manappuram Finance and the Adani group stocks.

The second place is physical settlement. A retail trader long on an Infosys future the day before expiry, distracted by a deal at work, finds the position rolling into delivery. The broker debits several lakh of contract value, the shares land in the demat the next day, and the trader spends the next morning hunting for buyers in cash to square off.

The third place is single-stock event risk. A weak quarterly result on Infosys is a few hundred basis points of move on the stock — a basis point is one-hundredth of a per cent, so a few hundred is a few per cent. The same move, multiplied by a full lot and divided by a thin margin, can be half the account in a single session.

The fourth place is liquidity. Out of the 200-plus stocks in the F&O segment, only a much smaller subset trade with spreads tight enough for a retail trader to enter and exit cleanly. The rest look attractive on paper, but try to exit a five-lot position in a thin name on a fast day and the slippage — the gap between the price you expected and the price you actually got — will teach the lesson on its own.

The fifth is position sizing. A Reliance lot eats ₹1.35 lakh of margin, so a trader with ₹6 lakh of capital is tempted to carry four lots.

That is about ₹27 lakh of single-name exposure on ₹6 lakh of capital, on a company whose price can move five per cent on a single quarterly result. One bad event and the account is not down. It is gone.

Stock futures are not a casino. The way most retail traders use them is.