Statute of Limitations

The IRS has 3 years from the later of the time you filed the return or the due date of the return to examine it and assess additional tax. For example, if you filed your 2016 tax return on March 15, 2017, then the IRS had until April 15, 2020 to examine the return. If you extended the 2016 tax return to October 15, 2017 and filed by that date, then the IRS has until October 15, 2020 to pick it for examination. Pretty soon most taxpayers can throw away the 2016 supporting documents.