Amended declarations.
(a)If, after a declaration is filed, the estimated tax is…#
(a) If, after a declaration is filed, the estimated tax is substantially increased or decreased by a change in income, an amended declaration shall be filed on or before the next date for payment of an installment of estimated tax. The remaining unpaid installments shall be proportionately increased or decreased as the case may be, to reflect any increase or decrease in the estimated tax by reason of such change.
(b)If an amended declaration is filed after September 15…#
(b) If an amended declaration is filed after September 15 and on or before the following January 15 and shows an increase in estimated tax, the increase shall be paid at the time of filing such an amended declaration. However, if such taxpayer files his annual income tax return with full remittance of tax due by January 31, he shall be relieved from filing such an amended declaration.