5. Employer's liability to deduct and pay tax on behalf of employees

The tax payable under this Act, by any person earning a salary or wage, shall be deducted by his employer form 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, where the employer is an officer of the State Government or the Central Government, the manner in which such employer shall discharge the said liability shall be such as may be prescribed:
Provided further that, whether any person earning a salary or wage-

a. is also covered by one or more entries other than entry 1 in the First Schedule and the rate of tax under any such other entry is more than the rate of tax under entry 1 in that schedule; or 
Rule 10, Form III , Form IV
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 get enrolled under sub-section (2) of section 6 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.