Understatement penalty.

A taxpayer has a reportable transaction understatement if the following calculation results in a positive number: 1. Multiply the taxpayer’s highest applicable tax rate under s. 71.06, 71.27, or 71.46, by the amount of any increase in Wisconsin taxable income that results from the difference between the proper tax treatment of a reportable transaction and the taxpayer’s treatment of the transaction as shown on the taxpayer’s tax return, including any amended return the taxpayer files before the date on which the department first contacts the taxpayer regarding an examination of the taxable year for which the amended return is filed. For purposes of this subdivision, the amount of any increase in Wisconsin taxable income for a taxable year includes any reduction in the amount of loss available for carry-forward to the subsequent year. 2. Add the amount determined under subd. 1. to the amount of any decrease in the aggregate amount of Wisconsin income or franchise tax credits that results from the difference between the proper tax treatment of a reportable transaction and the taxpayer’s treatment of the transaction as shown on the taxpayer’s tax return.

The secretary of revenue may waive or abate any penalty imposed under this subsection, or any portion of such penalty, if the taxpayer demonstrates to the department that the taxpayer had reasonable cause to act the way the taxpayer did, and in good faith, with regard to the tax treatment for which the taxpayer is subject to a penalty under this subsection and all facts relevant to the tax treatment are adequately disclosed in the filing under sub. (2), except that, if the taxpayer does not fully disclose such facts under sub. (2), the taxpayer’s penalty may be waived or abated under this paragraph if the taxpayer demonstrates to the department that the taxpayer reasonably believed that the tax treatment for which the taxpayer is subject to a penalty under this subsection was more likely than not the proper treatment and substantial authority exists or existed for the tax treatment for which the taxpayer is subject to a penalty under this subsection. Notwithstanding any other law or rule, a determination by the secretary of revenue under this paragraph may not be reviewed in any judicial proceeding.

The penalties under par. (a) apply to any reportable transaction understatement from a reportable transaction, including a listed transaction, entered into on or after January 1, 2001, or entered into prior to January 1, 2001, that reduced the taxpayer’s tax liability for taxable years beginning on or after January 1, 2001, for any taxable year for which the statute of limitations on assessment, including any extension provided under sub. (6), has not expired as of October 27, 2007.