Should the audit uncover a major error, the IRS has the ability to look at returns filed for earlier years as well. However, they don't usually go back farther than six years. The IRS tries to act on audits as quickly as possible.This means that most audits happen on returns filed within the last two years. Exceptions to the Three Year Statute of Limitations. The IRS has the right to audit back as far as six years if the taxpayer omitted more than 25% of their income for a single year.Taxpayers who leave out greater than $5,000 earned in foreign countries may also be audited as far back as six years. Not filing a tax return is not a good way to avoid an audit.hould the audit uncover a major error, the IRS has the ability to look at returns filed for earlier years as well. However, they don't usually go back farther than six years. The IRS tries to act on audits as quickly as possible.