Calendar Spreads in Futures Trading the USD INR Pair

Futures Calendar Spread

Currency futures contracts are generally expected to trade at a premium to the spot price. This is not a market anomaly but a predictable consequence of the cost of carry embedded within the standard futures pricing formula, a concept explored in detail within the Futures module of this series. When a futures contract deviates meaningfully from its fair value, the gap between the actual price and the theoretically correct price creates an arbitrage opportunity.

The principle is most easily understood through a simplified example. Suppose the spot price of an asset is Rs. 100, and applying the futures pricing formula produces a fair value of Rs. 105 for the corresponding futures contract. The no-arbitrage spread between spot and futures is therefore Rs. 5. Now suppose the futures contract is mispriced and trading at Rs. 98. The actual spread has widened to Rs. 7, creating a discrepancy of Rs. 2 relative to fair value. A trader who buys the futures at Rs. 98 and simultaneously sells the spot at Rs. 100 locks in this spread. As the contract approaches expiry, futures and spot prices converge, and the spread is captured as profit.

The reverse applies equally. If futures are trading above their fair value, a trader can short the futures and buy the spot, again locking in the excess spread until convergence occurs at expiry.

This logic is clean and well-established. However, executing spot-futures arbitrage in the USD-INR market is not practically accessible to most retail participants. The USD-INR spot market is the domain of banks, large financial institutions, and authorised dealers. Retail traders and individual investors operating through a stock broker on domestic exchanges do not have direct access to the spot market for currency pairs.

The practical alternative available within the currency derivatives segment is the Calendar Spread.

A calendar spread involves simultaneously taking positions in two futures contracts on the same currency pair but with different expiry dates. Rather than exploiting a discrepancy between spot and futures prices, the calendar spread seeks to profit from a discrepancy in the price relationship between a near-month contract and a far-month contract.

The foundational principle is straightforward. Because of the cost of carry, the far-dated futures contract should ordinarily trade at a higher price than the near-dated one. The August USD-INR contract, for instance, will almost always be priced above the July contract. A certain spread between the two is therefore expected and normal. The trading opportunity arises when this spread moves to a level that appears excessive or insufficient relative to what the interest rate differential and prevailing market conditions would justify.

Consider the following scenario. The USD-INR July futures contract is trading at Rs. 67.3075, and the August contract is trading at Rs. 67.6900. The current spread between the two contracts is calculated as follows.

Rs. 67.6900 minus Rs. 67.3075 equals Rs. 0.3825.

A trader who analyses the interest rate differential and prevailing market conditions concludes that a spread of Rs. 0.2000 is more appropriate, and that the current spread of Rs. 0.3825 is therefore inflated. The potential profit available from a reversion to the expected spread is as follows.

Rs. 0.3825 minus Rs. 0.2000 equals Rs. 0.1825.

To capture this opportunity, the trader simultaneously buys the July futures contract at Rs. 67.3075 and sells the August futures contract at Rs. 67.6900. This structure, where the near-month contract is bought and the far-month contract is sold, is known as a Futures Bull Spread. The opposing configuration, where the near-month contract is sold and the far-month contract is bought, is referred to as a Futures Bear Spread.

Once the Futures Bull Spread is in place, the trader monitors the spread between the two legs and looks to close the position when it narrows to Rs. 0.2000 or below. There are several scenarios through which this convergence can occur profitably.

The July leg rises whilst the August leg falls. The July leg rises whilst the August leg remains unchanged. Both legs rise, but the July leg rises at a faster rate than August. Both legs fall, but the August leg falls faster than July. The July leg remains unchanged whilst the August leg falls.

In each of these scenarios, the spread narrows, and the trader profits from the difference between the entry spread of Rs. 0.3825 and the exit spread.

A natural question follows: will the spread actually converge, and under what conditions is that likely to occur? The answer requires a thorough understanding of the specific spread being traded, including how it has behaved historically under comparable market conditions. This is where back testing becomes an essential discipline. By examining historical price data for the two contract series, a trader can assess how frequently and under what circumstances spreads of this magnitude have reverted to more typical levels, providing a statistical basis for the trade rather than relying on intuition alone.

Back testing as a methodology warrants its own dedicated treatment, which will be addressed separately. What the present chapter establishes is the structural simplicity of the calendar spread as a trading approach within the currency derivatives segment. The mechanics of entering and exiting a spread position through a standard trading platform are no more complex than placing two simultaneous orders, one long and one short, on contracts within the same currency pair.