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 returns and tax laws when auditing tax returns. An internal auditor would use records from a company's computerized payroll system and efficiency/effectiveness standards when reviewing payroll processing. Independent auditors are external and impartial, while internal auditors are internal employees who evaluate operations and compliance. OFAG auditors and IRS agents also have different roles and criteria than independent and internal auditors.