IRS Notice of Deficiency and Form 5564
An IRS Notice of Deficiency (Notice 3219A) is an official letter stating that you owe additional tax, which may include penalties and interest. It outlines the proposed adjustments and gives you 90 days to respond. Typically, you’ll receive IRS notice CP2000 first about a possible discrepancy. Form 5564, a waiver, comes with Notice 3219A.