Why not put on every field of the form "5th Amd"?
Let them make the argument that your refusal to incriminate yourself is illegal.
If you don’t answer their questions, they will calculate what they think you owe, and charge you for that. It will probably be larger than what you would normally owe if you just reported. They can also just audit you and subpoena all your records, and throw you in jail if you don’t comply.