What Is a Basis Trade? How Basis Trading Works

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A basis trade is a position that profits or loses from changes in the basis, the gap between the spot (cash) price of an asset and the price of a futures contract on that asset. The trader holds one side in the cash market and the opposite side in futures, so most of the exposure to the overall price level cancels out. What remains is a bet on how the spread between the two prices will move.

How the Futures Basis Is Measured

In agricultural markets, the convention is:

Basis = Cash price − Futures price

Suppose corn trades at $4.00 per bushel locally and the nearby futures contract trades at $4.25. The basis is −$0.25, usually called “25 under.” If cash were $4.30 against the same futures price, the basis would be +$0.05, or “5 over.”

A basis that moves toward a higher number (from −0.25 to −0.15, say) is said to strengthen. A move toward a lower number is said to weaken. Equity index and bond desks usually flip the sign and quote futures minus spot, so “widening” and “narrowing” can describe opposite outcomes depending on who is speaking. Check which convention a quote uses before deciding whether a change helps or hurts a position.

The gap between spot and futures mainly reflects the cost of carry: financing, storage and insurance for physical goods, minus any income the asset pays, such as dividends or coupons. Local supply and demand, transport costs and crop quality also move the cash side in physical markets. Near expiry, delivery makes the two prices meet, which is why the basis tends toward zero as a contract approaches its last trading day.

Long and Short the Basis

• Long the basis: own the cash commodity (or bond, or index basket) and sell futures. The position gains if the basis strengthens, meaning cash rises relative to futures.
• Short the basis: sell or commit to deliver cash later and buy futures. The position gains if the basis weakens.

A farmer who holds a growing crop and sells futures against it is long the basis in this sense. The hedge removes most of the risk from a general price drop, but the final selling price still depends on where the basis ends up.

Worked Example: A Grain Hedge (Hypothetical)

A farmer expects to sell corn in two months. Good weather raises the risk of oversupply and lower prices.

1. Today: cash $4.00, futures $4.25, basis −$0.25. The farmer sells enough futures to cover the expected harvest at $4.25.
2. Two months later: prices have fallen. Cash is $3.70, futures $3.85, basis −$0.15.
3. Close out: the farmer sells the corn at $3.70 and buys back the futures at $3.85. That produces a $0.40 per bushel gain on the futures.
4. Net price: $3.70 + $0.40 = $4.10 per bushel.

The result equals the original futures price plus the closing basis ($4.25 − $0.15). The $0.10 strengthening in the basis is the hedger’s gain compared with the −$0.25 basis at the start. If the basis had weakened to −$0.35 instead, the net price would have been $3.90. The hedge protected against the price fall but not against the basis move.

Basis Trades in Financial Futures

The same logic applies to stock index, interest rate and metals futures, where the trade is usually a cash-and-carry arbitrage. A simplified fair value for an index future is:

Futures fair value ≈ Spot × [1 + (r − d) × t]

Here r is the financing rate, d is the dividend yield and t is the time to expiry in years.

Hypothetical: index at 5,000, r = 5%, d = 2%, three months to expiry. Fair value ≈ 5,000 × 1.0075 = 5,037.50, a basis of 37.50 points (futures minus spot). If the futures trade at 5,060, an arbitrageur could buy the index basket, sell futures and lock in roughly 22.50 points before trading and financing costs. Convergence at expiry delivers the profit. A higher expected dividend lowers fair value and narrows the basis. If the dividend yield exceeds the financing rate, the futures can trade below spot.

In government bond markets, the Treasury basis trade pairs a long cash Treasury position, financed in the repo market, with short Treasury futures. Spreads are small, so the trade is typically run with heavy leverage. Forced unwinding of these positions was widely cited as a source of stress during the March 2020 Treasury market sell-off.

Limitations and Risks

• Basis risk: the hedge only works as well as the basis behaves. Local cash conditions, grade differences or a mismatch between the hedged asset and the contract can move the basis against you.
• Margin and leverage: the futures leg is marked to market daily. A profitable trade at expiry can still require cash for margin calls along the way, and leveraged positions may be forced out before convergence.
• Financing: carry trades depend on borrowing costs. A jump in repo or margin rates can erase a thin spread.
• Delivery features: bond futures let the short choose which eligible bond to deliver (the cheapest-to-deliver), which complicates the convergence math.
• Liquidity: exiting both legs at fair prices is harder in stressed markets. Contract volume and open interest give a partial read on depth.

Terms Often Confused With the Basis Trade

• Cost basis: the purchase price of an investment, used for tax and gain calculations.
• Basis points: hundredths of a percentage point, a unit for rates and yields.
• Basis risk: the risk inside a basis trade or hedge, not the trade itself.

FAQs

The Bottom Line

Hedgers in physical commodities and arbitrageurs in index, bond and metals futures rely on the basis behaving as expected. A hedge removes most exposure to a general price move, yet the final result still depends on where the basis ends up. Before entering, confirm which sign convention a quote uses and plan for daily margin calls, financing costs and thin liquidity that can force an exit before convergence.