Asset class classification is the practice of assigning every financial instrument a firm holds or trades to a category, such as equity, fixed income, cash, derivative, commodity, property or another alternative. The label is stored with other instrument reference data in the security master file, and it decides how the instrument is treated downstream: which valuation, risk and accounting rules apply, which limits it counts against and where it appears in client and regulatory reports.
Firms may use their own hierarchy, a data vendor's scheme, or a public standard such as the ISO 10962 classification of financial instruments code. Because different schemes group the same instrument differently, a convertible bond or a listed fund can sit in more than one asset class depending on the purpose. Consistent rules matter for asset allocation reporting and are a core part of security classification.