A sole proprietor is an individual who owns and operates a business on their own account, without using a separate legal entity such as a company or LLP. In legal practice, it describes the simplest form of business structure, where the business and the owner are treated as one and the same person for most legal and tax purposes. Across England and Wales, Scotland, Northern Ireland and Ireland, “sole trader” is the more common term in legislation and guidance, but “sole proprietor” is widely used descriptively in commercial contracts, banking documentation, leases and professional engagement letters. Key features include: unlimited personal liability for business debts and obligations; ownership of business assets in the individual’s name (or trading name); and direct responsibility for regulatory compliance, tax, employment and health and safety obligations. A sole proprietor can employ staff and enter into contracts, but always as an individual. The term is relevant when advising on risk allocation, security, guarantees, insolvency exposure, partnership formation, business sales and succession planning. Usage and legal effect are broadly consistent across the UK and Ireland, subject to differing tax regimes and registration requirements.