Arbitrage
The simultaneous purchase and sale of the same or equivalent security across different markets or instruments to lock in a profit from a pricing discrepancy, ideally with no net directional risk.
Definition
Arbitrage is the practice of exploiting price differences for the same or economically equivalent asset in different markets, forms, or time periods to generate a profit that is theoretically free of directional market risk. The most cited form in Indian markets is cash-futures arbitrage: when a stock's futures contract trades at a premium to the cash price that exceeds the fair cost of carry, an arbitrageur buys the stock in the cash segment and simultaneously sells the futures, locking in the spread as risk-free return that unwinds at expiry. Options arbitrage exploits deviations from put-call parity — if puts and calls of the same strike and expiry are mispriced relative to each other, a conversion or reversal position extracts the discrepancy. In reality, pure arbitrage opportunities in highly liquid Indian markets are fleeting and typically captured by high-frequency algorithms within milliseconds.
Why it matters
Arbitrage plays a critical role in market efficiency: it is the mechanism that keeps NSE and BSE prices aligned for cross-listed stocks, that keeps Nifty futures tracking the index, and that keeps option premiums consistent with put-call parity. For retail and institutional traders, the relevance is twofold. First, arbitrage mutual funds — a popular category in India — use cash-futures arbitrage to deliver near-risk-free returns taxed as equity (holding over 65% in equities), making them attractive for short-term parking of funds versus liquid debt funds. Second, understanding where arbitrage breaks down reveals mispricing opportunities: when basis (futures minus spot) widens unusually, it may signal stress or a large participant imbalance rather than a pure carry opportunity. The basis itself is a live indicator of market sentiment about future direction.
Formula
The fair value of a futures contract relative to its spot price is given by the cost-of-carry model: Futures Fair Value = Spot Price × e^(r − d) × T, where r is the risk-free rate, d is the expected dividend yield, and T is the time to expiry in years. Any futures price above this fair value represents a positive carry trade opportunity (buy spot, sell futures). For options, put-call parity states: Call − Put = Spot − PV(Strike). Violations of this relationship imply riskless profits from conversion (long put + long stock + short call) or reversal (long call + short stock + short put) positions — typically arbitraged away within seconds on liquid strikes.
Example
Suppose Infosys is trading at ₹1,800 in the NSE cash segment. The one-month futures contract is trading at ₹1,830, implying an annualised carry of approximately 20% — well above the current risk-free rate of 7%. An arbitrageur buys 1,200 shares (one lot) at ₹1,800 (total outlay ₹21,60,000) and simultaneously sells the futures at ₹1,830. At expiry, regardless of where Infosys trades, the futures and cash prices converge. The arbitrageur exits both legs, locking in ₹30 × 1,200 = ₹36,000 gross profit in one month. Accounting for brokerage, STT on delivery, and funding cost of the cash leg, the net return is lower — but still above the risk-free alternative, which is why the trade is executed.
Monitor basis and OI for arbitrage signals
Use TradePulse to track futures basis and open interest in real time, spotting unusual spread widening before it narrows.