Stamping of share certificates

Hi,

Company Incorporation- June 16, 2011.

The subscribed shares were not yet allotted to members in First Board Meeting. If the shares are allotted on August 18, 2011 via a Board circular, when is the stamp duty on share certificate required to pay? What is the time limit for the same as per company law and where is it mentioned?

Pls treat this as urgent.

Thanks.