How collateral re-use funds lending — vs fractional-reserve banking and DeFi leverage looping.
Rehypothecation is the re-use of collateral a client has pledged. It is easy to treat as a back-office funding detail, but it is closer to the reason secured lending exists at scale: the mechanism by which a firm turns a client's own collateral into the funding that lets the firm extend that client — and the market — cheap, capital-light credit.
The chain runs in one direction, and the direction matters.
The client's property, held by the firm as security. It is not the firm's asset.
client property · held as security · segregation rules attach hereThe cash the firm lent — a receivable, an asset on the firm's books. The receivable is what does the work: it licenses the re-use.
firm asset · the receivable licenses the re-useUnder SEC Rule 15c3-3, Regulation T and the hypothecation rules (8c-1 / 15c2-1), the firm may re-pledge the client's collateral up to 140% of that client's debit balance. The re-pledged slice goes to a funding venue — typically tri-party repo — which returns cash; that cash funds the client's intraday (daylight) overdraft, cured at next-morning settlement.
| Brake | Rule | Test | Limit |
|---|---|---|---|
| Per client | 15c3-3 | Possession-or-control test | Reusable collateral ≤ 140% of that client's debit balance |
| Firm-wide | 8c-1 / 15c2-1 | Aggregate-indebtedness test | Total pledged ≤ the sum of all client debits · the 140% figure appears nowhere in this test |
Rehypothecation is one of three mechanisms that all run the same engine: an asset is re-used down a chain, each hop retaining a fraction, and the retained fraction caps a geometric series at 1 / brake. What differs is not the math but whose asset is re-used and who keeps the leverage.
The same number plays the same role in all three mechanisms — it is the brake that stops the series.
| Dimension | Fractional-reserve lending | Rehypothecation (prime broker) | DeFi leverage looping |
|---|---|---|---|
| What is re-used | Depositors' cash | Clients' pledged collateral | Your own collateral, recursively |
| Who re-uses it | The banking system | The intermediary firm | One actor, levering itself |
| The brake | Reserve ratio | Haircut + 140%-of-debit cap | Collateral factor / LTV |
| Multiplier | 1 / reserve ratio | ~1 / haircut, capped at 140% × debit | 1 / (1 − LTV) |
| Credit funds | Loans economy-wide | Short-dated intraday credit to clients | Your own levered position |
| Backstop | Central bank + deposit insurance | Client's segregated excess + reserve tiers | Over-collateralization + liquidation |
| Failure mode | Bank run (maturity mismatch) | Collateral-chain unwind | Liquidation cascade / de-peg spiral |
Rehypothecation is not the liquidity itself — it is the funding leg that makes offering the liquidity cheap and capital-light. A firm could lend purely from its own capital; it simply could not do so at competitive rates or at market scale. Three levers explain why re-use is so central.
Without re-use, the firm funds every client loan out of its own capital, which caps how much credit it can extend. Rehypothecation turns the client's collateral into the funding source, letting a dealer run a large secured-lending book on thin capital.
The matched book: the collateral effectively finances the loan it secures.Secured funding raised through rehypothecation is far cheaper than unsecured borrowing, and the cheaper funding passes through to the client as a tighter financing spread. Clients frequently permit re-use in exchange for a lower rate.
The rehypothecation discount: the client's liquidity is cheaper because they allow re-use.High-quality collateral (Treasuries) is scarce; re-use lets the same bond back several credit relationships at once — empirically a first-order driver of how much secured credit the whole system can supply.
The collateral analog of the money multiplier. The multi-trillion-dollar daily repo market runs on it.In short, rehypothecation is the difference between a boutique that lends its own capital and a prime broker that intermediates the market.
The same re-use that amplifies credit supply in good times amplifies runs in bad times. When collateral velocity collapses, secured credit dries up quickly — the transmission channel visible in 2008 and in the Lehman failure.
The 140% cap and segregation-in-fact protected client property. LBI's clients were ported to other firms in days.
clamped re-use · 140% + possession-or-controlUnlimited, title-transfer re-use left LBIE's clients frozen as unsecured creditors for years.
unlimited re-use · title transfer · no per-client capThat contrast is the thesis behind Ascend's design: keep the liquidity-provision upside — re-using client collateral to fund intraday credit — while making the fragility structurally impossible. Onchain, the 140% cap and per-client segregation stop being policy and become contract invariants.