You could be charged with wilfully failing to timely file and/or pay taxes, which is a misdemeanor offense. If convicted, you could face a prison term of up to 1 year for each unfiled and/or unpaid year.
You could also be charged with tax evasion. This offense is a felony that is penalized by up to 5 years in federal prison for every year you wilfully evaded tax by not filing your return or payment on time.