Reports of alleged fraud to the IRS need to be made in writing, using the appropriate IRS form. You need to discuss this with your lawyer. If the alleged fraud involved returns that you were joint on, you could be causing problems for yourself as well. In addition, if the IRS does get interested in these allegations, any claims they may have take priority over most others, potentially including yours. You could be cutting off your nose to spite your face.
Answered on Sep 26th, 2013 at 9:32 AM