What it means
The basis is simply the cash price minus the futures price. In a normal market the futures price sits above the cash price by roughly the cost of carry, which covers financing, storage and insurance, less any income the asset produces along the way.
When the futures premium exceeds the true cost of carry, a trader can buy the physical asset, finance it, and simultaneously sell futures to lock in the higher forward price. The profit is known at the outset, which is why the trade is usually described as cash-and-carry arbitrage.
This matters to businesses that never trade a contract, because it is the mechanism that keeps futures honest. Hedgers depend on cash and futures moving together, and basis traders are the ones who force that relationship back into line whenever it drifts.
The risks are not zero despite the arbitrage label. Financing costs can rise, margin calls on the futures leg can demand cash long before the profit arrives, and in government bond markets the same trade is often run with heavy borrowing that turns a small adverse move into a large loss.
The Treasury basis trade is the best-known example, exploiting tiny gaps between cash government bonds and bond futures. Because the gaps are so small, participants borrow heavily in repurchase markets to make the returns worthwhile, which is why regulators watch the activity as a potential source of instability.
In practice
Real-world examples.
Example
A commodity trading house buys physical copper and sells three-month futures whenever the forward premium exceeds warehousing and financing costs. The desk earns a small, predictable spread and unwinds the position at delivery.
Example
A hedge fund buys cash Treasury bonds and sells the corresponding bond futures, funding the bonds in the repurchase market. The gap is a fraction of a percentage point, so the fund uses substantial borrowing, and a sudden rise in repurchase rates forces it to cut the position quickly.
Example
A grain merchant with silo space buys wheat at harvest and sells deferred futures when the carry in the market exceeds its own storage and interest costs. It is effectively being paid by the market to hold inventory it would have stored anyway.
Formula
Calculation
Basis = Cash price - Futures price; Cash-and-carry profit per unit = Futures price - Cash price - Cost of carry.
A trader sees gold quoted at $2,000 an ounce for immediate delivery and $2,040 an ounce for delivery in six months. Financing the purchase costs 3% a year, which over six months is 2,000 x 0.03 x 0.5 = $30 an ounce, and storage and insurance add $4 an ounce, giving a total carry of 30 + 4 = $34. The futures premium is 2,040 - 2,000 = $40, so the locked-in profit is 40 - 34 = $6 an ounce. On a 500-ounce position that is 500 x 6 = $3,000, earned with no exposure to the gold price at all. The margin is thin enough that it vanishes entirely if financing rises from 3% to about 3.6% before the position is closed.Case study
Seen in the real world.
Calloway Straits Capital is an invented fund used purely as an illustrative example. Its strategy was straightforward: buy cash bonds, sell the matching futures, and collect a spread of roughly 0.08% a year, borrowing about twenty dollars against every dollar of its own capital to make that spread worth having.
For three years the trade worked exactly as modelled. Then a burst of market stress caused lenders in the repurchase market to demand more collateral at the same time as the futures leg generated margin calls, and both cash demands arrived within the same week.
In this fictional account the fund was forced to sell bonds into a falling market to raise cash, turning an arbitrage with a known profit into a real loss. The illustrative point is that basis trading is not risk-free but funding-risk-heavy: the price relationship usually holds, and the danger lies in whether you can stay financed until it does.
Watch out
Common mistakes.
- Calling basis trading risk-free arbitrage, when it carries financing, margin and liquidity risk even though the price outcome is largely locked in.
- Ignoring the cost of carry when comparing a cash price with a futures price, which makes a perfectly normal spread look like a profit opportunity.
- Sizing the trade off the expected spread alone, when the amount of borrowing required is what determines whether a small adverse move becomes fatal.
Questions
People also ask.
What is the basis in basis trading?
The cash price minus the futures price, which in a normal market reflects the cost of carrying the asset to the delivery date.
Why do basis trades use so much borrowing?
Because the spreads are extremely small, so returns only become attractive once the position is many times the trader's own capital.
Does basis trading help or harm markets?
In normal conditions it keeps cash and futures prices aligned, which helps hedgers, but the heavy borrowing behind it can amplify stress when funding markets tighten.
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