The formal name for this document is IRS CP3219B Notice or Statutory Notice of Deficiency. It sounds very ominous but it would not be the first contact you had from the IRS regarding their intent to assess a tax deficiency. You would have first received a notice requesting that you check your tax return against information that the IRS has received regarding your financial matters. The notice is not a bill; however, you can pay the additional tax if you agree with the IRS. If not, then you should take further steps to file a dispute. For more information read, “Taxes From A To Z (2013): N Is For Notice Of Deficiency.”