If an enrolled person or a registered employer fails, without reasonable cause, to make payment of any amount of tax within the time or date specified in the notice of demand, the prescribed authority may, after giving him a reasonable opportunity of being heard, impose upon him a penalty not exceeding fifty per centum of the amount of tax due: 

Provided that no penalty shall be imposed under this section upon a person who has paid the tax due from him under this Act in accordance with the provisions of section 9A:

Provided further that where a registered employer being a company, fails to make payment of tax under this section, any director, manager, secretary, or other officer of such company who was in charge of, and responsible to, the company for the conduct of business of such company and knowingly concerned with such non-payment of tax, shall be equally liable for the said penalty.