Margin Financing

Margin financing is borrowing money from a broker, using the securities in your account as collateral. It lets investors buy more than their cash alone would allow, and it lets professional funds run leveraged strategies through prime brokers. Brokers earn interest on these loans, and margin lending is a major source of revenue for many of them. For borrowers, margin magnifies both gains and losses and adds interest costs and the risk of forced selling.

How margin loans work#

How brokers price margin#

Rates are typically tiered: larger balances get lower rates. Rates vary enormously between brokers, from close to benchmark rates for some low cost brokers to many percentage points above for others. Professional clients and funds negotiate rates with prime brokers based on size and relationship. See Prime Brokerage.

Haircuts and collateral quality#

Brokers lend less against riskier collateral. A large, liquid stock might support a loan of 50% or more of its value, while a volatile small cap might support much less, and some securities are not marginable at all. Brokers can raise requirements at any time, often during market stress or for individual volatile stocks, which can trigger sudden margin calls. See Liquidity Risk.

Risks of margin financing#

Margin and market crashes#

Margin debt amplifies market cycles. In 1929, many investors bought stocks with as little as 10% down; falling prices triggered margin calls and forced selling that deepened the crash. Regulation T, introduced later, set higher initial margin requirements. Aggregate margin debt figures, published by FINRA, are watched as a sign of speculative leverage. See The 1929 Crash and Systemic Risk.

Other forms of financing#

Using margin responsibly#

1. Borrow modestly, well below the maximum allowed.
2. Compare rates across brokers; differences are large.
3. Keep a cash buffer to meet calls without forced selling.
4. Stress test your account for a sharp market fall. See Stress Testing and Scenario Analysis.
5. Never use margin for money you cannot afford to lose.

Frequently asked questions#

What is margin financing?#

Borrowing money from a broker to buy securities, using the securities in the account as collateral and paying interest on the loan.

How is margin interest calculated?#

Usually daily on the loan balance, at a rate based on a benchmark plus a spread that typically falls as the balance rises.

Can a broker sell my stocks without asking?#

Yes. If your account falls below margin requirements, the broker can liquidate positions without notice to protect its loan.

Next, learn how funds calculate their value in Fund Accounting and NAV.