Examination of the accounting records, financial position, and compliance of an individual or organization with objective standards. A tax audit is a review by the IRS of the tax return filed by a taxpayer including books and records to substantiate the entries on the return.
An audit is a systematic and independent examination of books, accounts, statutory records, documents and vouchers of an organization to ascertain how far the financial statements as well as non-financial disclosures present a true and fair view of the concern. Wikipedia