GST refund claim on exports ?

You can apply for refund provided that you have an ITC in credit ledger.

you need to apply from GST Portal.

After login > Services > Refund > Application for Refund.

select option "Refund of ITC on Export of Goods & Services without Payment of Tax"

provide the details. after that you need to upload pdf file of GSTR 3B Return copy, GSTR 2A/2B in which showing invoices filed by party. and other details.

after apply department will process the same. you need to also calculate the refund amount as per calculation provided by Government. (Export turnover/ Total Turnover ) X ITC.