How it works
Legally, a repo is two trades. Today you sell me a bond for cash. Simultaneously you agree to buy it back tomorrow, or in a week, at a slightly higher price. Economically it is a secured loan, and the difference between the two prices is the interest. The reason anyone bothers with the sale-and-repurchase framing rather than writing a normal loan agreement is insolvency law: because the lender legally owns the collateral, it can sell it immediately if the borrower fails, without waiting for a court.
The haircut is where the leverage lives. Illustratively, if you post $100m of Treasuries and the lender advances $98m, the haircut is 2% and you have funded a $100m position with $2m of your own money. Do it again with the bonds you just bought, and again after that, and $2m of capital supports a very large book. Fifty-to-one is arithmetic, not exaggeration, when the haircut is two points.
Most repo is overnight, which means the entire structure is refinanced every morning. That works on the mornings it works. The lender can raise the haircut, or simply decline to roll, at which point the borrower must find cash the same day or sell the collateral. Because the collateral is usually the most liquid thing on the balance sheet, it gets sold first, which pushes prices down, which raises the haircut, which forces more selling. That is the whole of a repo run in one sentence.
Cleared versus bilateral
When a repo clears through a central counterparty, the haircut is standardised, exposures net against each other, and a regulator can see the aggregate. Non-centrally cleared repo — bilateral repo — is a private contract. The haircut is negotiated, the terms are undisclosed, and no single party knows how much a given borrower has already borrowed from everyone else. A fund whose collateral falls in value receives a margin call from each of its five lenders separately, on the same morning, and none of them knows about the other four.
The market is moving toward the dark half. We wrote on 20 August that the BIS reported non-bank financial institutions now account for more than 40% of non-centrally cleared euro-denominated cash-borrowing repo, up from less than 30% at the end of 2020, and expects that share to keep rising.
Why it matters to this crash
Repo is the funding leg of the , which Federal Reserve research put at roughly $830bn as of September 2025 — about double the early-2020 peak. That matters for the specifically. The marginal holder of US right now is not a pension fund that will sit through a drawdown; it is a repo-financed relative-value position that has to be refinanced tomorrow morning at whatever haircut the lender feels like.
It also sits at the exact point where the current policy mix is being tested. As we wrote on 19 August, the Treasury is retiring long bonds and funding it with bills while the New York Fed has cut reserve management purchases to zero for 14 August to 14 September. More bills to finance, no new reserves to finance them with. Whether that works shows up in one number: , the rate at which Treasuries are actually repo'd overnight, sat at 3.65% and had not moved as of that piece.
More broadly, most of what we cover is credit that does not reprice, because nobody has to it. Private loans, data-centre project bonds, insurance balance sheets, litigation ABS. Repo is the opposite. It reprices every single day, which is why funding markets are usually where a slow credit problem becomes a fast one. The complex can carry unmarked losses for quarters. It cannot carry a failed roll for an afternoon.
What would make this dangerous
SOFR printing persistently above 's administered rates, rather than the occasional quarter-end spike, would say dealer balance sheets have run out of room to intermediate. Watch it against the 3.65% we noted on 19 August.
widening on Treasury collateral specifically. Treasuries are the collateral everything else is priced off; if lenders start demanding four points instead of two against government bonds, every levered position in the system is instantly half the size it was, and the deleveraging happens through sales.
A leveraged borrower failing in bilateral repo, where the lenders discover simultaneously that they were each the fifth-largest creditor. The BIS number measures how much of the market is now in the dark. It does not measure how much any one borrower owes.
Collateral that turns out to have been pledged twice. The SEC's case against Tricolor's former executives alleges exactly that failure — hundreds of millions of dollars of loans double-pledged. Repo's entire safety mechanism is the assumption that when you take the bond, you have the bond.