GST Refunds are available in case of exports and inverted rate structures ( where inward supplies are at higher rate than the outward supplies). The refund can be claimed with payment of tax as well as withuot payment of tax however the supplier needs to furnish a Letter of Undertaking in case of supplies without payment of tax. 

Currently provisional refunds are granted to upto 90% of the amount claimed subject to submission of correct documents which is processed within 7 days of the claim. 

My True Books offers its expertise around filing for refunds by qualified CAs and Industry experts.