The tax payable under this Act by any person earning salary or wage, shall be deducted by his employer from the salary or wage payable to such person, before such deduction has been made or not, when the salary or wage is paid to such person be liable to pay tax on behalf of all such person:
Provided that, if the employer is an officer of Government, the State Government notwithstanding anything contained in this Act, prescribe by the rules the manner in which such employer shall discharge the said liability:
[Provided further that, where any person earning a salary or wage-
(a) Is also covered by one or more entries other than entry 1 in Schedule I and the rate of tax under any such other entry is more than the rate of tax under entry 1 in that Schedule, or
(b) Is simultaneously engaged in employment of more than one employer, and such person furnished to his employer or employers a certificate in the prescribed from declaring, inter alia, that he shall get enrolled under sub-section (2) of section 5 and pay the tax himself, than the employer or employers of such person shall not deduct the tax from the salary or wage payable to such person and such employer or employers, as the case may be, shall not be liable to pay tax on behalf or such person.]