The supplier may asked to issue revised invoice on a date when you have become a registered taxable person.

I am not convinced with the reply. As invoice is raised on say 28.06.17, material has left our godown and we have already accounted the invoice on even date and the customer receives the invoice and material after 05.07.17   

A registered taxable person shall be entitled to take, in his electronic credit ledger, credit of Value Added Tax [and entry tax] in respect of inputs received on or after the appointed day but the tax in respect of which has been paid before the appointed day, subject to the condition that the invoice or any other tax paying document of the same was either received or recorded in the books of accounts of such person within a period of thirty days from the appointed day: PROVIDED that the aforesaid period of thirty days may, on sufficient cause being shown, be extended by the competent authority for a further period not exceeding thirty days.
(2) The said registered taxable person shall furnish a statement, in such manner as may be prescribed, in respect of credit that has been taken under sub-section (1).