(a) The total estimated tax may be paid on or before the fifteenth day of the fourth month of the income year of the taxpayer; provided, individuals whose gross income from farming or fishing for the income year can reasonably be expected to amount to at least two-thirds (⅔) of the total gross income from all sources for the income year, may file and pay the estimated tax on or before the fifteenth day of the first month after the close of the income year; however, if such taxpayer files a completed income tax return on or before the first day of the third month following the close of the income year and pays the tax shown to be due thereon, it shall not be necessary to file or pay any estimated income tax.

(b) At the election of the taxpayer, individuals may pay the tax in equal installments of one-fourth (¼) on or before the fifteenth day of the fourth month of the income year, one-fourth (¼) or before the fifteenth day of the sixth month of the income year, one-fourth (¼) on or before the fifteenth day of the ninth month of the income year, and one-fourth (¼) on or before the fifteenth day of the first month after the close of the income year. Corporations may elect to pay the tax in installments of one-fourth (¼) on or before the fifteenth day of the fourth month of the income year, one-fourth (¼) on or before the fifteenth day of the sixth month of the income year, one-fourth (¼) on or before the fifteenth day of the ninth month of the income year, and one-fourth (¼) on or before the fifteenth day of the twelfth month of the income year.

(c) In the case of a taxpayer who makes an amendment to the tax estimate, the tax payments due after such amendment shall be adjusted either up or down to conform to the amended estimate of tax.

(d) In the case of a taxpayer who first meets the requirements subsequent to the fifteenth day of the fourth month of the income year, and not later than the fifteenth day of the ninth month of the income year the estimated tax may be paid in equal installments with the first installment being due at the time the taxpayer first meets the requirements and an installment being due on each subsequent regular tax payment date for the income year as prescribed in paragraph (b) of this section. If the taxpayer meets the requirements subsequent to the fifteenth day of the ninth month of the income year, the estimated tax shall be paid in full at that time.

(e) Any tax payment due under the provisions of this article may be paid by the taxpayer in advance of the date prescribed herein for the payment thereof.

(f) In the case of a corporate taxpayer, acting in good faith, that is paying its estimated tax in accordance with paragraph (b) of this section and that is unable to calculate with certainty the amount of estimated tax payable as the installment due on the fifteenth day of the twelfth month of the income year, the commission may allow the taxpayer to pay as its total estimated taxes an amount less than ninety percent (90%) of the tax liability; however, this provision shall not affect the amount of the tax liability that will be due on income for that year or the penalties which may be imposed for failure to file estimated tax returns and for underestimates that occur regarding installments due at any time other than the fifteenth day of the twelfth month of the income year.