What is the test for a good faith misunderstanding defense in a tax case?

requires negating [1] a defendant's claim of ignorance of the law or [2] a claim that because of a misunderstanding of the law, he had a good-faith belief that he was not violating any of the provisions of the tax laws. This is so because one cannot be aware that the law imposes a duty upon him and yet be ignorant of it, misunderstand the law, or believe that the duty does not exist.

Cheek v. United States, 498 U.S. 192, 202, 111 S.Ct. 604, 112 L.Ed.2d 617 (1991) (emphasis added).

There is, then, a difference between an "ignorance" defense and a "good faith misunderstanding" defense. In order to rely on a good faith defense, the defendant must in fact have some "belief;" either that her own understanding was correct, or that she in good faith relied on the tax advice of a qualified tax professional. See United States v. Bishop, 291 F.3d 1100, 1106-07 (9th Cir.2002).