A security agreement is a contract under which a borrower or other obligor grants a security interest over assets in favour of a lender or other secured party to secure payment or performance of obligations. In practice it sets out the collateral, the secured obligations, creation of the security (for example, fixed and floating charges in England and Wales and Northern Ireland, or standard securities and fixed/floating charges in Scotland, or charges in Ireland), and the enforcement rights on default.The expression “security agreement” is descriptive rather than a defined legislative term in the UK and Ireland, though it is commonly used in finance documents and commentary. It typically appears as a standalone debenture or charge, or as a schedule or section within a wider facility agreement.Key issues for practitioners include validity and attachment/creation of the security, perfection (for example, Companies House or CRO registration, and in Scotland delivery or registration in appropriate registers), priority against competing creditors, and insolvency outcomes. Usage is broadly consistent across England and Wales, Scotland, Northern Ireland and Ireland, although the underlying security devices and registration regimes differ by jurisdiction.