Sale and purchase date are different?

vinayak c. chavan (CPT passed) (1011 Points)

03 October 2017  

We are pvt ltd com based in mumbai. We are selling a product worth rs 3 lacs to one of our customer with invoice dated 30.09.2017 but we have purchased same product on 03.10.2017. Will it be of to book purchase in Oct 2017. Please suggest its impact relating to GST.