(1) In connection with any extension of the time for filing a return under s. 220.222(2), the taxpayer shall file a tentative tax return and pay, on or before the date prescribed by law for the filing of such return, determined without regard to any extensions of time for such filing, an amount estimated to be the balance of its proper tax for the taxable year after giving effect to any estimated tax payments under s. 220.33 and any tax credit under s. 220.721. (2) The department shall by regulation prescribe the manner and form for filing tentative returns.
(3) Interest on any amount of tax due and unpaid during the period of any extension shall be payable as provided in s. 220.809. The taxpayer shall also be liable for a penalty in an amount determined at the rate of 12 percent per year upon the amount of any underpayment of the tax due. 