If a taxpayer has a reportable transaction understatement for any taxable year, there shall be added to the tax an amount equal to 20 percent of the amount of such understatement.
Subsection (a) shall be applied by substituting “30 percent” for “20 percent” with respect to the portion of any reportable transaction understatement with respect to which the requirement of section 6664(d)(3)(A) is not met.
For purposes of this section, the terms “reportable transaction” and “listed transaction” have the respective meanings given to such terms by section 6707A(c).
This section shall not apply to any portion of an understatement on which a penalty is imposed under section 6663.
This section shall not apply to any portion of an understatement on which a penalty is imposed under section 6662 if the rate of the penalty is determined under subsections (h) or (i) of section 6662.
Except as provided in regulations, in no event shall any tax treatment included with an amendment or supplement to a return of tax be taken into account in determining the amount of any reportable transaction understatement if the amendment or supplement is filed after the earlier of the date the taxpayer is first contacted by the Secretary regarding the examination of the return or such other date as is specified by the Secretary.