(a) Assessment date.-The amount of tax which a return shows to be due, or the amount of tax which a return would have shown to be due but for a mathematical or clerical error, shall be deemed to be assessed on the date of filing of the return (including any amended return showing an increase of tax). In the case of a return properly filed without computation of tax, the tax computed by the commissioner shall be deemed to be assessed on the date on which payment is due. If a notice of deficiency has been mailed, the amount of the deficiency shall be deemed to be assessed on the date specified in subsection (b) of section six hundred eighty-one if no petition to the division of tax appeals is filed, or if a petition is filed, then upon the date when a determination or decision rendered in the division of tax appeals establishing the amount of the deficiency becomes final. If an amended return or report filed pursuant to section six hundred fifty-nine concedes the accuracy of a federal change or correction, any deficiency in tax under this article resulting therefrom shall be deemed to be assessed on the date of filing such report or amended return, and such assessment shall be timely notwithstanding section six hundred eighty-three. If a notice of additional tax due, as prescribed in subsection (e) of section six hundred eighty-one, has been mailed, the amount of the deficiency shall be deemed to be assessed on the date specified in such subsection unless within thirty days after the mailing of such notice a report of the federal change or correction or an amended return, where such return was required by section six hundred fifty-nine, is filed accompanied by a statement showing wherein such federal determination and such notice of additional tax due are erroneous. Any amount paid as a tax or in respect of a tax, other than amounts withheld at the source or paid as estimated income tax, shall be deemed to be assessed upon the date of receipt of payment, notwithstanding any other provisions.(b) Other assessment powers.-If the mode or time for the assessment of any tax under this article (including interest, additions to tax and assessable penalties) is not otherwise provided for, the tax commission may establish the same by regulations.(c) Estimated income tax.-No unpaid amount of estimated tax shall be assessed.(d) Supplemental assessment.-The tax commission may, at any time within the period prescribed for assessment, make a supplemental assessment, subject to the provisions of section six hundred eighty-one where applicable, whenever it is ascertained that any assessment is imperfect or incomplete in any material respect.(e) Cross reference.-For assessment in case of jeopardy, see section six hundred ninety-four.