Title II — TAX ON INCOME to which a declaration is required under Subsection (A) shall be paid in four (4) installments. The first installment shall be paid at the time of the declaration and the second and third shall be paid on August 15 and November 15 of the current year, respectively. The fourth installment shall be paid on or before May 1536 of the following calendar year when the final adjusted income tax return is due to be filed. (C) Definition of Estimated Tax. — In the case of an individual, the term ‘estimated tax’ means the amount which the individual declared as income tax in his final adjusted and annual income tax return for the preceding taxable year minus the sum of the credits allowed under this Title against the said tax. If, during the current taxable year, the taxpayer reasonably expects to pay a bigger income tax, he shall file an amended declaration during any interval of installment payment dates. SEC. 75.  Declaration of Quarterly Corporate Income Tax. — Every corporation shall file in duplicate a quarterly summary declaration of its gross income and deductions on a cumulative basis for the preceding quarter or quarters upon which the income tax, as provided in Title II of this Code, shall be levied, collected and paid. The tax so computed shall be decreased by the amount of tax previously paid or assessed during the preceding quarters and shall be paid not later than sixty (60) days from the close of each of the first three (3) quarters of the taxable year, whether calendar or fiscal year. SEC. 76.  Final Adjustment Return. — Every corporation liable to tax under Section 27 shall file a final adjustment return covering the total taxable income for the preceding calendar or fiscal year. If the sum of the quarterly tax payments made during the said taxable year is not equal to the total tax due on the entire taxable income of that year, the corporation shall either: (A) Pay the balance of tax still due; or (B) Carry-over the excess credit; or (C) Be credited or refunded with the excess amount paid, as the case may be. In case the corporation is entitled to a tax credit or refund of the excess estimated quarterly income taxes paid, the excess amount shown on its final adjustment return may be carried over and credited against the estimated quarterly income tax liabilities for the taxable quarters of the succeeding taxable years. 36 As amended by Section 20 of the TRAIN Law. Previous deadline for the fourth installment was April 15 of the following calendar year. To clarify, the deadline for filing the annual income tax return and payment of the income tax payable therein is still April 15 of the succeeding calendar year pursuant to Section 51(C)(1) of this Code. National Internal Revenue Code of 1997 (as amended by the TRAIN Law, RAs 11256, 11346 and 11467) 93