Arbitrage in F&O means buying a stock in the cash market and selling its futures contract at the same time, or the other way round, to pocket the price gap between the two. This works because a stock’s futures price and its cash price must meet on expiry day. It is called low risk, not risk-free, since costs such as brokerage, margin, and taxes can shrink the profit if execution is slow.

What Is Arbitrage in F&O?
How Arbitrage in F&O Works
Practical Example With Numbers
Key Features of F&O Arbitrage
Advantages of Arbitrage Trading
Risks and Limitations
Tips for Beginners
Arbitrage vs Directional Trading
Common Mistakes to Avoid
Who Should Use This Concept
Conclusion
Frequently Asked Questions

Ever noticed that a stock’s price in your trading app is a little different from its futures price on the same screen? That small gap is where arbitrage traders make their money. Arbitrage in F&O is the practice of buying a stock in the cash market and selling its futures contract at the same time, so the trader locks in the price difference instead of guessing where the stock will go next. This blog explains how the strategy works, what it actually costs once you account for taxes and brokerage, and where beginners tend to slip up.

What Is Arbitrage in F&O?

Arbitrage in F&O means buying a stock in the cash market and selling the matching futures contract at the same time, or doing the reverse, to capture the price difference between the two. It works because a stock’s futures contract and its cash market shares must trade at the same price on the day the futures contract expires.

Here is why the gap shows up in the first place. A futures price is not simply a copy of the stock price. It also carries the cost of holding that stock until expiry, known as the cost of carry. If a trader had to borrow money to buy the stock and hold it, that borrowing cost is built into the futures price. When this cost is priced too high or too low compared to what it should be, an arbitrage opportunity opens up.

There is one rule beginners often miss. SEBI does not allow buying a stock on one exchange and selling it on another exchange on the same day unless the shares are already sitting in your demat account, a restriction detailed in the official NSE circular on securities transaction rules. So the older version of arbitrage, where traders bought on NSE and sold on BSE within the same day, is mostly not possible anymore for shares you do not already own. Most arbitrage trading in India today happens between the cash market and the futures market on the same exchange, a version covers in detail in its blog on cash-futures arbitrage.

How Arbitrage in F&O Works

Track the price gap. Watch the cash market price and the futures price of the same stock through the day.
Work out the fair futures price. Take today’s stock price and add the interest cost you would pay if you borrowed money to hold that stock until expiry. This gives you a rough idea of what the futures price should be.
Compare this fair value with the actual futures price. If the actual price is higher than the fair value, the futures contract is overpriced and worth selling. If it is lower, the opposite trade applies.
Place both trades together. Buy the stock in the cash market and sell the same quantity in futures, matching the exact lot size fixed by the exchange. Both orders need to go in within seconds of each other, or the gap can shrink before you finish.
Hold the position until expiry, since the futures price and cash price are designed to meet on that day.
Close both positions and work out the profit. Subtract brokerage, Securities Transaction Tax, and any borrowing cost from the gap you locked in at entry to get your real profit.

Practical Example With Numbers

Reliance Industries has an exchange fixed lot size of 500 shares per futures contract. Based on Reliance’s actual price range in early July 2026, where the stock has been trading close to ₹1,310 in the cash market with its near-month futures moving between roughly ₹1,307 and ₹1,320 on the same day, here is how a typical trade could look.choiceindia+2

Assume a trader buys 500 shares in the cash market at ₹1,310 each, spending ₹6,55,000. At the same time, the trader sells one futures lot at ₹1,318, worth ₹6,59,000. The gap locked in at entry is ₹8 per share, or ₹4,000 for the full lot.

Now here is where costs come in. Securities Transaction Tax on equity delivery is 0.1% on both the buy and sell side of the cash market trade, while STT on selling a futures contract is 0.05% of the trade value as of April 1, 2026. On this trade, that works out to roughly ₹655 STT on the cash buy, another ₹655 STT when the shares are eventually sold, and about ₹330 STT on the futures sale. Add brokerage and small exchange charges, and the total costs come to around ₹1,750.nseindia+1

Item	Amount
Cash market buy (500 shares at ₹1,310)	₹6,55,000
Futures sell (500 shares at ₹1,318)	₹6,59,000
Gross gap locked in	₹4,000
STT and brokerage costs (approximate)	₹1,750
Net profit	₹2,250

Notice that the actual profit is little more than half the gross gap once real costs are included. This is the part many beginners skip when they calculate arbitrage returns on paper, and it is exactly why the strategy needs large volumes to be worthwhile, not just a wide-looking price gap.

Key Features of F&O Arbitrage

Two legs, one trade. The strategy always involves a cash market position and a futures position taken together, never one without the other.
Profit is mostly fixed at entry. Once both legs are placed, the outcome is largely decided rather than dependent on which way the stock moves later.
Needs matching lot sizes. The futures lot size, fixed by the exchange, has to match the shares bought in the cash market exactly, or the hedge breaks.
Capital-heavy. Since both legs need real funding, arbitrage usually needs more capital than a plain intraday trade in one direction.
Time-bound. The trade only makes sense until the futures contract expires, since that is when the price gap is guaranteed to close.

Advantages of Arbitrage Trading

Less exposure to market direction. A sharp rally or fall in the stock does not change the locked-in profit much, since both legs move together.
Useful for shares you already hold. Investors sitting on long-term holdings can use arbitrage to earn a bit extra without selling their shares.
More opportunities during volatile phases. Price gaps between cash and futures tend to widen when markets swing sharply.
A calculable outcome. Unlike a directional bet, the rough profit can often be worked out before placing the trade.

Risks and Limitations

Execution risk. If the cash and futures orders do not go in almost together, the price gap can shrink or disappear before the trade is complete.
Costs eat into thin margins. Brokerage, STT, and margin funding costs can turn a promising-looking gap into a small or even negative return, as the earlier example shows.
Liquidity problems in smaller stocks. Futures contracts on mid-cap and small-cap stocks often trade in low volumes, making it hard to enter or exit large positions without moving the price yourself.
Regulatory limits. Same-day buying and selling of a stock across two different exchanges is restricted unless the shares are already in your demat account, which rules out the older cross-exchange version of this strategy.
Overconfidence with position size. Since the strategy is often described as low risk, beginners sometimes take positions larger than their capital can support, which increases the damage if execution goes wrong.

Tips for Beginners

Start with large-cap, high-volume stocks such as Reliance or ICICI Bank, since their cash and futures prices tend to move together more reliably.
Work out the fair futures value yourself before trusting the visible gap. A gap that looks large on screen can shrink once costs are included.
Add up brokerage, STT, and margin funding costs before deciding a trade is worth taking. As shown earlier, costs can take away almost half the gross gap.
Check the margin required for both legs on your broker’s margin calculator before placing the trade, not after.
If you cannot place both orders within a few seconds by hand, look for basket order tools instead of doing it leg by leg.
Keep the expiry date marked, since the profit is only locked in once the futures contract expires and both prices meet.

Arbitrage vs Directional Trading

Parameter	Arbitrage Trading	Directional Trading
Time horizon	Held till futures expiry, usually a few weeks	Intraday to a few days
Risk level	Lower, hedged between two legs	Higher, it depends entirely on price movement
Capital needed	Higher, since both legs need full funding	Can start smaller
What you own	A stock position plus an opposite futures position	Usually just one open position
Main goal	Capture a price gap	Bet on which way the price moves

Common Mistakes to Avoid

Skipping the cost calculation. Traders see a gap and jump in without subtracting brokerage and STT, only to find the real profit is much smaller than expected.
Wrong lot size matching. Buying a slightly different quantity than the futures lot size leaves part of the position unhedged, turning a safe trade into a risky one.
Placing legs separately. Buying the stock first and placing the futures order a minute later gives the market time to move against you.
Ignoring margin needs. Underestimating the margin required for the futures leg can lead to a forced square off by the broker before expiry.
Trading tiny price gaps. Not every visible gap is worth trading. After costs, some gaps leave no real profit at all, as the Reliance example shows.

Who Should Use This Concept

Arbitrage suits traders with enough capital to fund both legs comfortably, access to fast order execution, and the patience to hold a position until expiry rather than exit early for quick gains. It also works well for long-term investors who want to earn a bit more on shares they already hold, without giving up ownership of those shares.

It is less suitable for beginners trading with small capital or those still learning how margin and lot sizes work, since a small execution mistake can turn a safe-looking trade into a loss. New traders are often better off first understanding how futures contracts and margin requirements work before attempting this strategy.

Conclusion

Arbitrage in F&O works by buying a stock in the cash market and selling its futures contract at the same time, capturing the gap between the two prices instead of betting on where the stock is headed. That gap exists because cash and futures prices must meet on expiry day, but as the Reliance example shows, taxes and brokerage can take away close to half the gross profit if you are not careful with the numbers. For a beginner, the real skill is not spotting a price gap on screen. It is working out whether that gap still holds up once every cost is subtracted.