Treasury Basis Trades and How They Unwind

The Treasury basis trade profits from a tiny cash-futures gap using heavy repo leverage, and 2020 showed how fast it can unwind.

A Treasury basis trade buys a cash Treasury bond and simultaneously sells the corresponding Treasury futures contract, capturing the small pricing gap between the two while the position is financed almost entirely with borrowed money through repo. The trade is a bet on convergence rather than on the direction of rates, but the leverage required to make a tiny basis worth trading is exactly what turned an orderly relative value strategy into a source of forced selling across the Treasury market in March 2020.

A Treasury futures contract allows the short side to deliver any bond from a defined basket of eligible Treasury securities, and the bond that is cheapest to deliver into the contract sets the effective relationship between the futures price and the price of that specific cash bond. The basis is the difference between the cash bond's price and the futures price, adjusted by a conversion factor that accounts for the delivered bond's coupon and maturity relative to the contract's notional standard.

In a well-functioning market, the basis stays close to the cost of carrying the cash bond to the futures delivery date, meaning the coupon income earned on the bond minus the financing cost paid in repo, plus a small premium for the short's delivery option. When the basis trades wider than that carry-implied level, a fund can buy the cheaper cash bond, sell the richer futures contract, and expect the two prices to converge as the delivery date approaches, locking in the difference.

The basis itself is typically only a few basis points wide, far too small a spread to generate a meaningful return on capital if the position were funded entirely with a fund's own equity. The trade only becomes attractive once financed with repo borrowing against the cash bond as collateral, which lets a fund control a position many multiples the size of its actual capital, since Treasury repo haircuts are small and Treasury securities are the most easily financed collateral in the market, a mechanism covered in more detail in repo markets and their role in funding.

That leverage is what makes basis trading a repo-funding-dependent strategy rather than a pure relative value trade. A fund's ability to hold the position, and to hold it through any period of temporary widening before convergence, depends entirely on its repo counterparties continuing to offer financing at stable rates and haircuts, which is a dependency that is easy to overlook when the basis itself looks like a low-risk, market-neutral trade.