The basis trade: at its highest per the Fed, moribund per the market

On 22 June 2026, a Federal Reserve note X-rayed the hedge funds’ Treasury book: $4 trillion of gross exposure, including a basis trade estimated at $830 billion, nearly double its 2020 peak. Three weeks earlier, the specialist press was announcing the slow death of that same arbitrage, rendered barely profitable. A trade at its peak and out of breath at the same time: the paradox deserves decoding.

The basis trade is one of those invisible cogs we only talk about when it breaks. It contributed to the Treasury-market panic of March 2020, when the Fed had to buy hundreds of billions of dollars of debt to restore order. Since then, regulators and central bankers watch it. We described its mechanics in our reference piece, the basis trade at the heart of US debt. What is new is the quantified snapshot the Fed has just delivered, and the tension between what its data say and what the market says.

The bet, in brief

Let us recall the idea in one sentence. The price of a cash Treasury bond and that of its futures contract diverge slightly. A fund buys the security in cash, sells the future, and pockets the gap, the basis, at expiry. The gap is tiny, a few basis points, so it is amplified by leverage of 15 to 20 times, obtained by financing the purchase on the repo market, where cash is borrowed overnight against the security as collateral. The trade earns a steady income as long as funding stays cheap and volatility contained. It becomes dangerous when these two conditions reverse at the same time.

The Fed’s X-ray

The note, signed by economist Phillip Monin, breaks down for the first time with this precision the $2.4 trillion of hedge funds’ long Treasury positions, as of September 2025. The basis trade is its first brick: about $830 billion, or 35% of these long positions. Then come matched-maturity positions ($395 billion), curve-steepness bets ($375 billion) and swap-spread arbitrage ($305 billion).

Two figures give the measure of the phenomenon. The basis trade is today nearly double its early-2020 peak, the one that preceded the liquidity crisis. And hedge funds now hold about 8.5% of all US debt in private hands, against 4.5% in early 2023. A player that was a twentieth of the market now weighs nearly an eleventh.

The moribund-basis paradox

Here is the tension. At the very moment the Fed documents this record, practitioners bury the trade. Per Risk.net, the basis has lost its allure: spreads become too tight, under the inflow of capital that chases them, and a repo funding cost that has risen. As a result, the trade’s net income, the gap between what it earns and what its funding costs, has thinned to the point that many managers consider the operation finished.

The two observations contradict each other only in appearance. Size measures a stock of positions accumulated over years; profitability measures the flow they generate today. A trade can be both enormous and barely remunerative: it is even the most uncomfortable situation, the one where massive positions earn almost nothing, and where the slightest setback tips the balance toward the exit. An arbitrage that no longer pays is an arbitrage one is tempted to unwind, and an unwind at this scale is never done quietly.

Why the concentration worries

Because the real fragility is not size alone, it is concentration. The Fed note says it plainly: the 50 largest funds carry about 90% of these exposures, and the combination of a large scale, a strong concentration and high leverage creates a potential for systemic stress. When a few players hold the same positions with the same leverage, they tend to sell at the same time.

This is not a theoretical worry. In April 2025, swap-spread arbitrage, the basis trade’s cousin, saw about $60 billion of positions unwind abruptly in a few sessions, under a volatility spike. Apollo’s chief economist, Torsten Slok, warned as early as April 2026: this level of leverage exposes global bond markets to a shock if the positions were forced to unwind. Apollo says it is, moreover, reducing its own risk and building cash.

Who will buy the debt if the bet retreats

A more discreet angle deserves attention. By financing the purchase of cash Treasuries, the basis trade makes hedge funds an important marginal buyer of US debt, at the very moment the Treasury issues record amounts of it. If the arbitrage retreats, for lack of profitability or after a shock, a source of demand disappears from the auctions. The relay is not obvious, and its absence would be paid in higher yields. It is one of the reasons for the awakening of the term premium, that extra yield demanded to hold long debt, which we analysed in our piece on the awakening term premium. The basis trade is not only a stability risk; it is also, by implication, a pillar of financing the federal state.

The wildcard of mandatory clearing

A regulatory deadline can reshuffle the cards. The SEC mandates central clearing of Treasury transactions: cash from end December 2026, repo from end June 2027, after a one-year delay granted in 2025. By going through a clearing house like FICC, recently joined by CME, positions gain in transparency and flow netting, but face more systematic margins. For the basis trade, the effect is ambiguous: clearing can make it safer by reducing counterparty risk, or amputate it by raising its funding cost. In both cases, it will not leave it unchanged.

How the bet can unwind

Three outcomes emerge, to be held as analyst hypotheses and not forecasts.

The first is a gentle deflation. The trade no longer earning, funds lighten it gradually, the hedge-fund share of Treasuries recedes, and the arbitrage goes out of fashion without causing a tremor. It is the outcome Risk.net’s observation implies: a basis that dies slowly is a basis that does not break.

The second is a reshaping by regulation. The mandatory-clearing timeline transforms the trade’s conditions before a market shock does. Depending on the margin setting, the arbitrage contracts, shifts to other players or changes form. The transition itself carries a risk, if it forces position adjustments within a narrow window.

The third is the forced unwind, the scenario everyone dreads. A volatility spike, a margin call, a brutal move in yields, and the most leveraged positions unwind in disaster. To meet the margins, funds sell their Treasuries, which pushes yields up, which triggers new margin calls: the March 2020 spiral, bigger. It is not the most probable scenario, but it is the one whose cost would be heaviest, and it is the reason the Fed, the OFR and the FSB keep an eye on it.

The serious objections are not lacking

One must guard against catastrophism, and several arguments plead for calm. The basis trade renders a real service: by linking the cash price and the futures price, it maintains the coherence of a $31 trillion market and provides liquidity to Treasury auctions. Without it, the US state would finance itself at a slightly higher cost. The Fed also has a net it did not have in 2020, the Standing Repo Facility, a permanent window where primary dealers can obtain cash against Treasuries, precisely to prevent a repo drought from degenerating. And a basis trade that deflates on its own, for lack of profitability, reduces the risk instead of increasing it: it is an orderly exit, not a panic.

This reassuring reading nonetheless has its blind spots. The Standing Repo Facility has never been tested in a real storm, and nothing guarantees the deflation is slow: a barely profitable trade is a trade hanging by a thread, not a safe trade.

In sum

The Fed note and the market’s verdict do not contradict each other: they illuminate two faces of the same object. The basis trade is simultaneously bigger than ever and less remunerative than ever, a massive stock backed by a drying flow. It is an unstable configuration by nature, without being an immediate alarm. The most probable remains a gradual retreat, aided by the clearing timeline. The most costly would be a disorderly unwind, in a debt market already heavy with issuance. Between the two, the deciding variable is not the displayed size, it is the speed at which fifty funds will decide, or be forced, to exit at the same time.

Sources

1. Federal Reserve, FEDS Notes, Phillip J. Monin, “Decomposing Hedge Funds’ U.S. Treasury Exposures”, 22 June 2026: gross exposure of $4trn ($2.4trn long, $1.6trn short), basis trade ~$830bn (35% of longs, nearly double the 2020 peak), matched maturity $395bn, steepness $375bn, swap spread $305bn, 50 funds = ~90%, hedge funds at ~8.5% of private Treasuries: https://www.federalreserve.gov/econres/notes/feds-notes/decomposing-hedge-funds-u-s-treasury-exposures-20260622.html
2. Bloomberg, “Fed Says Basis Trade Key Driver of Hedge Fund Treasury Exposure”, 24 June 2026: https://www.bloomberg.com/news/articles/2026-06-24/fed-says-basis-trade-key-driver-of-hedge-fund-treasury-exposure
3. Risk.net, “Treasury basis trade loses its allure as returns shrink”, June 2026: spreads too tight and rising funding cost: https://www.risk.net/markets/7963653/treasury-basis-trade-loses-its-allure-as-returns-shrink
4. Bloomberg, “Apollo’s Slok Warns Hedge Fund Treasury Bets Risk Market Shock”, 17 April 2026: hedge funds at ~8% of the Treasury market ($31trn), against 3% five years ago: https://www.bloomberg.com/news/articles/2026-04-17/apollo-s-slok-warns-hedge-fund-treasury-bets-risk-market-shock
5. SEC, extension of the Treasury mandatory-clearing timeline (cash on 31 December 2026, repo on 30 June 2027) and approval of CME as a clearing house: https://www.sec.gov/newsroom/speeches-statements/uyeda-statement-update-continuing-work-toward-treasury-clearing-implementation-122325
6. Financial Stability Board, “Vulnerabilities in Government Bond-backed Repo Markets”, 4 February 2026: https://www.fsb.org/uploads/P040226.pdf
7. l0g, The Treasury basis trade: the leveraged arbitrage at the heart of US debt.
8. l0g, US debt and the awakening of the term premium.
9. l0g, Repo and SOFR market guide.