In April 2013, Dan is audited by the IRS for the year 2011. During the course of the audit, the agent discovers that Dan's deductions for business travel and entertainment are unsubstantiated and a $600 deficiency assessment is proposed for the tax year 2011. The agent also examined some prior year returns. The agent discovers that Dan failed to report $40,000 of gross business income on his 2009 return. Gross income of $60,000 was reported in 2009. The agent also discovers that Dan failed to file a tax return in 2004.
Will the statute of limitations prevent the IRS from issuing a deficiency assessment for 2011, 2009, or 2004? Explain.