We have discussed appeals in the past and one certainly might be able to appeal this notice of additional tax.  We need to know the answer to some questions first, such as: Has the tax actually been assessed or has the taxpayer simply been notified that he might owe this additional tax?  Also, if it has been assessed how long ago was the notice sent?  Generally one can appeal IRS decisions if he does so within 30 or 60 days.  Different types of adverse decisions have different appeal periods.  Was the assessment the result of an audit?  If not, perhaps we might ask for an audit to prove the tax is not owed. We have to know what the IRS based their claim on.