The severance occured in 2021 and the taxpayer was unaware that the ex employer was withholding on his wages at one rate and his severance at 22%.  He is underpaid by a substantial amount of money and he contacted his employer to understand what I just described.  The employer told him that a) 22% is what they are required to withhold b) led him to believe that by attaching his paystubs to the tax return his severance would only be taxed at 22% regardless of his tax bracket.  I cannot find anything in a Publication or elsewhere supporting the latter.