Federal law sets out time limits, or statutes of limitations, for the IRS can pursue taxpayers who fail to file their tax return.
The government can only bring criminal charges against a nonfiler within 6 years of the date the tax return was due. For example, after April 15, 2014, you can’t be prosecuted for failing to file a 2007 tax return that was due on April 15, 2008.
But there is NO deadline on the IRS for going after nonfilers and imposing civil penalties, in addiition to any taxes owed. In other words, while you can’t be put in jail for not filing a 2007 tax return, you will forever owe the IRS a return, assuming you earned enough income to meet the minimum filing requirements for that year. And penalties and interest on unfiled tax returns run forever.