For purposes of section 6511, any return filed before the last day prescribed for the filing thereof shall be considered as filed on such last day. For purposes of section 6511(b)(2) and (c) and section 6512, payment of any portion of the tax made before the last day prescribed for the payment of the tax shall be considered made on such last day. For purposes of this subsection, the last day prescribed for filing the return or paying the tax shall be determined without regard to any extension of time granted the taxpayer and without regard to any election to pay the tax in installments.
If any overpayment of income tax is, in accordance with section 6402(b), claimed as a credit against estimated tax for the succeeding taxable year, such amount shall be considered as a payment of the income tax for the succeeding taxable year (whether or not claimed as a credit in the return of estimated tax for such succeeding taxable year), and no claim for credit or refund of such overpayment shall be allowed for the taxable year in which the overpayment arises.
Notwithstanding subsection (a), for purposes of section 6511 any payment of tax imposed by chapter 23 which, pursuant to section 6157, is made for a calendar quarter or other period within a calendar year shall, if made before the last day prescribed for filing the return for the calendar year (determined without regard to any extension of time for filing), be considered made on such last day.