(2) A person who pays any instalment or instalments of advance tax under sub-section (1), may increase or reduce the amount of advance tax payable in the remaining instalment or instalments to accord with his estimate of his current income and the advance tax payable thereon, and make payment of the said amount in the remaining instalment or instalments accordingly.

(3) In the case of a person who has been already assessed by way of regular assessment in respect of the total income of any previous year, the Assessing Officer, if he is of opinion that such person is liable to pay advance tax, may, at any time during the financial year but not later than the last day of February, by order in writing, require such person to pay advance tax calculated in the manner laid down in section 209, and issue to such person a notice of demand under section 156 specifying the instalment or instalments in which such tax is to be paid.

(4) If, after the making of an order by the Assessing Officer under sub-section (3) and at any time before the 1st day of March, a return of income is furnished by the assessee under section 139 or in response to a notice under sub-section (1) of section 142, or a regular assessment of the assessee is made in respect of a previous year later than that referred to in sub-section (3), the Assessing Officer may make an amended order and issue to such assessee a notice of demand under section 156 requiring the assessee to pay, on or before the due date or each of the due dates specified in section 211 falling after the date of the amended order, the appropriate percentage, specified in section 211, of the advance tax computed on the basis of the total income declared in such return or in respect of which the regular assessment aforesaid has been made.

(5) A person who is served with an order of the Assessing Officer under sub-section (3) or an amended order under sub-section (4) may, if in his estimation the advance tax payable on his current income would be less than the amount of the advance tax specified in such order or amended order, send an intimation in the prescribed form to the Assessing Officer to that effect and pay such advance tax as accords with his estimate, calculated in the manner laid down in section 209, at the appropriate percentage thereof specified in section 211, on or before the due date or each of the due dates specified in section 211 falling after the date of such intimation.

(6) A person who is served with an order of the Assessing Officer under sub-section (3) or amended order under sub-section (4) shall, if in his estimation the advance tax payable on his current income would exceed the amount of advance tax specified in such order or amended order or intimated by him under sub-section (5), pay on or before the due date of the last instalment specified in section 211, the appropriate part or, as the case may be, the whole of such higher amount of advance tax as accords with his estimate, calculated in the manner laid down in section 209.