An independent CPA firm would use a company's historical financial statements and accounting standards when auditing financial statements. An IRS auditor would use tax records and tax laws when auditing tax returns. An internal auditor would use records of the computerized payroll system and efficiency/effectiveness standards when auditing the payroll processing system. Independent auditors are external and impartial, while internal auditors are internal but still impartial, and revenue agents enforce tax compliance. Financial statement audits examine financial records according to accounting standards, operational audits examine internal operations according to efficiency standards, and compliance audits examine adherence to regulations. Auditors verify accuracy while accountants prepare records, and auditors require expertise in evaluation and investigation beyond account preparation.