The tax (***) paid on goods purchased by a person who is subsequently required to be registered under section 14 due to new liabilities or levies or gets voluntary registration under this Act or the rules made thereunder, shall be treated as input tax, provided that such goods were purchased by him from a registered person against an invoice issued under section 23 during a period of thirty days before making an application for registration and constitute his verifiable unsold stock on the date of compulsory registration or on the date of application for registration or for voluntary registration:

Provided that where a person imports goods, the tax paid by him thereon during a period of ninety days before making an application for registration shall be treated as an input tax subject to the condition that he holds the bill of entry relating to such goods and also that these are verifiable unsold or un-consumed stocks on the date of compulsory registration or on the date of application for registration or for voluntary registration.