Margin & CollateralMedium

The system's real constraint: not who has capital, but who can post it today. Every crisis of the last twenty years ran through this page.

4 min read · 762 words · Updated 4 Sep 2026

The two margins

Every leveraged or derivative position runs on collateral, and the vocabulary splits in two:

• Initial margin (IM) — the deposit that opens the position: a buffer sized to potential future moves (clearing houses compute it from stress scenarios). It parks; you get it back.
• Variation margin (VM) — the daily (now often intraday) cash settlement of gains and losses. It flows: your loss is wired to the winner today, not netted at expiry.

The distinction sounds bureaucratic and decides crises: VM is a liquidity demand with a same-day deadline. A position can be profitable at maturity and still kill you on Tuesday — the definition of the 2022 UK pension (LDI) crisis and of the European utilities' 2022 margin squeeze (both hedged correctly, both nearly illiquid).

Leverage arithmetic: the distance to the exit

Haircuts: leverage set by the lender

• A haircut is the discount on collateral's value: 2% haircut → borrow 98 against 100 → maximum leverage 50× (the repo calculator inverts it).
• Haircuts are procyclical: calm markets shrink them (leverage builds), stress widens them (leverage unwinds, forcibly). The system's gearing is set not by regulators but by thousands of collateral schedules.
• Rehypothecation lets collateral be reused down a chain — one Treasury securing several loans. Efficient plumbing; in failure, several claimants and one bond (a 2008 lesson re-taught on-chain by FTX).

The margin spiral — the system's core feedback loop

• Prices fall → VM calls and wider haircuts → forced selling to raise cash → prices fall further → repeat. Brunnermeier & Pedersen formalised it; 2008, March 2020 and the 2022 gilt crisis performed it.
• The sale is forced, so it ignores value — which is why margin-driven crashes overshoot and why "who is levered, funded how" beats "what is it worth" as the crisis question.
• Case study, LDI 2022: UK pensions hedged rates with leveraged gilt derivatives. Gilts crashed → VM due same-day → pensions sold gilts to fund it → gilts crashed further — until the Bank of England bought the spiral to a halt. Every step was contractually correct.
• Case study, Archegos 2021: one family office, equivalent positions at five prime brokers, none seeing the whole. One margin call started the race; the slowest banks (Credit Suisse: $5.5bn) financed the lesson about margin being counterparty-blind.

Practitioner rules

• Measure liquidity against VM, not against P&L: the question is never only "am I right?" but "can I fund the path while being proven right?"
• Know every trigger in advance: maintenance levels, haircut reset clauses, collateral eligibility — the exits are written in the docs, at signing, when nobody reads them.
• Treat margin capacity as a position: unused borrowing power in calm markets is the asset that buys the fire-sale prices the spiral produces — the whole trade of "be the liquidity when others need it".