If you've supplied goods or services to an SEZ unit and paid tax, you can apply for a refund using form RFD 01. The specific option to select is 'Refund on account of Supplies to SEZ unit/ SEZ Developer (with payment of tax)'. To support your claim, ensure your tax invoices are endorsed by the SEZ unit.
12 August 2020
Based on your query, I can understand that you have supplied goods/service to sez unit with payment of tax. In that case you can you need to file RFD 01 online under the option "Refund on account of Supplies to SEZ unit/ SEZ Developer (with payment of tax)".
13 August 2020
True,I didn't notice that it is with payment of tax.You have to get your tax invoices endorsed from the SEZ in order to file the refund of GST.