Hi
All GST returns have to be filed showing invoices as export without payment of GST. Currently, GSTR3B and GSTR1 needs to be filed; GSTR3B before 20th of subsequent month and GSTR1 quarterly.
You will have to pay GST on invoices dated before the date of LUT and claim refund, if applicable.
I assume your turnover is less than INR 1.5 crores.