An audit which is compulsory by law is:

An audit is an independent examination of financial information of any entity, whether profit-oriented or not, irrespective of its size or legal form, when such an examination is conducted with a view to expressing an opinion thereon. A Statutory Audit is precisely what the question describes: an audit that is legally mandated by a statute or law. Companies, especially public ones, are often required by law (e.g., Companies Act in many countries) to have their financial statements audited annually by an independent external auditor. This ensures transparency, accountability, and protects the interests of stakeholders like shareholders, creditors, and the public.

• Government Audit refers to audits conducted by government agencies on public sector entities or programs, ensuring compliance and efficiency, but it's not a general legal mandate for all entities like a statutory audit.
• Internal Audit is an independent, objective assurance and consulting activity designed to add value and improve an organization's operations. It is typically voluntary and performed by employees within the organization, focusing on internal controls and risk management, not a legal compulsion for external reporting.
• Cost Audit specifically examines cost records to ascertain their accuracy and adherence to cost accounting principles. While it can be compulsory for certain industries or companies under specific regulations, it is not the overarching legal requirement for financial statement examination that a statutory audit represents.