(a) In the event that there is a failure to pay an estimated tax installment within the term established or that the payment made to cover the estimated tax installment is incomplete, unless it is shown to the satisfaction of the Secretary that this was due to a reasonable cause and not due to willing carelessness, there shall be an addition to the taxes of ten percent (10%) of the unpaid amount of such installment. Provided, That the first year in which the special tax on gross income takes effect, this penalty shall not apply with respect thereto, insofar as the provisions of Section 1061.21 of this Code are complied with. For these purposes, the estimated tax shall be:(1) Ninety percent (90%) of the tax of such taxable year, in the case of individuals, other than farmers, who exercise an option under § 30262(a) of this title or sixty-six and two-thirds percent (66⅔%) of the tax so determined, in the case of those farmers, or(2) the total of the tax determined, as reported in the income tax return filed for the preceding year, whichever is less. History —Jan. 31, 2011, No. 1, § 6041.09, retroactive to Jan. 1, 2011; June 30, 2013, No. 40, § 51.