A cost bill is a detailed, itemised statement of legal costs and expenses prepared for assessment, taxation or recovery between parties, or for approval of a solicitor’s fees by the court. It typically sets out professional fees, disbursements (such as counsel’s fees, experts’ charges and court fees), VAT and any uplifts or success fees, with dates, descriptions of work and time spent.In England and Wales and Northern Ireland, a bill of costs (or costs schedule) is commonly used in detailed assessment or summary assessment of costs under the Civil Procedure Rules or equivalent; “cost bill” is a descriptive term rather than a defined statutory expression. In Scotland, an account of expenses serves a similar function; in Ireland, a bill of costs is prepared for adjudication under the Legal Services Regulation Act 2015.Cost bills are central to costs litigation, solicitor–client fee disputes, and enforcement of costs orders. Accuracy, proper categorisation, and compliance with applicable rules and practice directions are critical, as defects can lead to reductions on assessment, disallowance of items, or adverse costs consequences.