Glossary
Margin: definition
Margin is the cash or securities a firm requires against a leveraged position. It is a buffer for the firm. It is not a fee, and it is not the maximum you can lose.
In practice
Initial margin opens the position. Maintenance or variation margin keeps it open as prices change. If you cannot meet a call, the firm can liquidate. House margin can exceed exchange minimums. On securities, margin also means a loan, with interest. On futures and CFDs it means collateral on a contract. The glossary entry is short on purpose; the margin guide walks through calls and pattern-day-trader rules.
A worked example
You post 5,000 as margin on a futures position whose contract exposure is far larger. A move against you of more than that buffer requires more cash the same day, or the position is reduced for you.
Sources and review
Written by: WiT Markets Editorial. Writes and structures WiT Markets pages. Separates a sourced fact from a cell that is Not confirmed.
Review: Editorially reviewed. This is not a qualified specialist review and it is not a legal sign-off.
Last reviewed: . Next review due . The date is an editorial pass. It is not a live check of every third-party fee.
Regulatory and official sources
- FINRA — checked 13 October 2026
- Financial Conduct Authority — checked 13 October 2026
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