How far back can the IRS go to audit a tax return?

There is a statute of limitations that limits the IRS to three years to audit a return. But there are exceptions. If income is underreported by 25%, the limit is extended to six years. If you file a fraudulent return, there is no limit. If you fail to file Form 8938 “Specified Foreign Financial Assets” when required, then the three-year limit doesn’t start until the form is filed.