Cash-and-Carry Arbitrage

A cash-and-carry arbitrage is a market-neutral strategy in which a trader simultaneously buys an asset in the spot market and sells a futures contract on the same asset, locking in a riskless profit if the futures price exceeds its theoretical fair value. The strategy is especially common in stock index futures, bonds, currencies, and commodities, and has historically been a powerful mechanism for maintaining efficient pricing between cash and derivatives markets.

The economics: fair value and the basis

The basis is the simplest version of the idea: Futures Price = Spot Price + Basis. In an efficient market, the basis should equal the cost of carry, which is the cost of holding the spot asset until futures expiry.

For a stock or stock index, the cost of carry is the interest rate paid to finance the purchase, minus the dividend yield received while holding the shares. If you buy the S&P 500 Index at spot price 5,000 and pay 5% to finance the purchase, but the index yields 2% in dividends over six months, your cost to carry for six months is roughly 1.5% of the spot price.

Therefore, a six-month futures contract should trade near 5,000 × 1.015 = 5,075. If it trades at 5,100, it is overpriced by 25 basis points. Buying the index and shorting the future captures that 25 basis points, minus transaction costs.

The anatomy of a riskless trade

Here is the execution:

1. Today (Day 0): Simultaneously:

   • Buy all 500 stocks in the S&P 500 Index (or an index fund) at spot price 5,000.
   • Sell one six-month futures contract at 5,100.
   • Finance the stock purchase at 5% per annum.

2. At Futures Expiry (Day 180): The futures contract converges to the spot price of the index (by definition, futures converge to spot at expiry). Say the index is then 5,050.

   • Close the futures position at 5,050 (sell leg is bought back for 5,050).
   • Sell the stocks at 5,050 (they are worth spot price).
   • Repay the loan of 5,000 plus six months of interest: 5,000 × 1.025 = 5,125.

3. Profit: Futures leg: Sold at 5,100, closed at 5,050 = +50. Stock leg: Bought at 5,000, sold at 5,050 = +50. Financing cost: -125. Net = -25. This is a loss.

Wait—this is the no-arbitrage case. Futures price was correctly set at 5,100. Let’s reprice: if futures had traded at 5,150 instead, the profit would be +150 (futures) + 50 (stock gain) - 125 (interest) = +75 basis points riskless gain.

Why liquidity and transaction costs matter

In theory, the trade is riskless once both legs are on. In practice, an arbitrageur must:

1. Buy 500 individual stocks (or transact in a large block), incurring bid-ask spreads and market impact.
2. Sell futures quickly before the spot price moves.
3. Hold the position for months, paying financing costs and managing margin.

For a mega-fund with $10 billion under management, these costs might be 2–5 basis points—leaving room for profit if the mispricing is larger than 10 basis points. For a retail trader, transaction costs might be 100+ basis points, eliminating all profit.

This is why cash-and-carry arbitrage is predominantly an institutional sport. Firms with prime brokerage relationships, algorithmic execution, and minimal borrow costs profit; everyone else is priced out.

Reverse cash-and-carry: the flip side

When futures are underpriced relative to fair value, an arbitrageur executes the reverse: short the spot asset and buy the futures. This strategy is less popular because short selling has higher costs and borrowing restrictions than buying. But in liquid markets (equities, currencies), reverse arbitrage is feasible and essential for tight pricing.

Why it matters for price discovery

Cash-and-carry arbitrage is not glamorous, but it is crucial. If index futures are overpriced relative to the spot index, arbitrageurs buy the index and sell futures. This buying pressure lifts the spot price and selling pressure pushes down the futures price, closing the gap. The market is kept honest.

Conversely, if futures are underpriced, shorts are covered and futures bought, closing the gap from the other direction. The mechanism is invisible to most traders, but it is relentless. Basis trading profits are measured in hundreds of basis points per year, but trillions of dollars of spot-futures mispricing is eliminated in the process.

Commodities: storage and convenience yield

Cash-and-carry works differently in commodities. To carry crude oil, you must pay storage, insurance, and financing costs. You receive no “dividend” unless the market is in backwardation (near futures cheaper than far futures), in which case the convenience of owning physical supply is a benefit valued by refineries and traders.

An oil trader buys crude oil at spot and sells six-month futures, locking in the cost of carry plus storage. If the future is priced above this, the trade is profitable. If it is priced below—which can happen in contango—the trader incurs a loss. This dynamic is why oil futures curves tell a story about supply and demand expectations.

Bonds and repo

In government bond markets, cash-and-carry is executed via the repo market. A trader borrows bonds, sells them, and simultaneously buys a bond future to be delivered later. The financing cost is the repo rate, which can be much cheaper than the nominal interest rate. Basis trading in bonds is a staple of fixed-income desks.

See also