The tax payable under this Act by any person earning a salary or wage shall be deducted by his employer from the salary or wage payable to such person, before such salary or wage is paid to him, and such employer shall, irrespective of whether such deduction has been made or not when the salary or wage is paid to such persons, be liable to pay tax on behalf of all such persons:

 Provided that if the employer is an officer of Government, the State Government may, notwithstanding anything contained in this Act, prescribe by rules the manner in which the 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 the Schedule and the rate of tax under such entry or any of such entries is higher than that in entry 1, or

(b) Is simultaneously engaged in employment of more than one employer, and such person furnishes to his employer or employers a certificate in the prescribed form declaring, inter alia, that he shall obtain a certificate of enrolment under sub-section (2) of section 5 and pay the tax himself, then 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 of such person.