What is an audit? There's one main goal of an audit: to make sure that someone has paid the right amount of federal income taxes, and that income and deductions are reported correctly. In some cases, an audit could result in someone paying more in taxes. In 2019, the IRS reported that audits resulted in $17.3 billion worth of additional taxes paid. How far back can the IRS audit? The IRS can only conduct tax audits on fairly recent tax returns. Generally, audits only happen for the last three tax years. However, audits can go back as far as six years in special circumstances.