Gst refund received on export of goods on payment of duty whereas export sales proceeds not realized

In GST,  Exports are treated as ZERO RATED SUPPLY. simply means ZERO Rate of TAX on the supply.

Exports can be made with either of the options, with payment of TAX (either by utilizing available ITC balance or by actual payment)  OR Without payment of TAX under Letter on Undertaking. 

We get the refund of TAX paid if we opt for the 1st option. This refund is not contingent on the realization of the Export proceeds.  

Hence there is no question of recovery of TAX upon write-off of the Export proceeds. 

Recovery needs to be checked for Export Incentives  given under Foreign Trade Policy under which bank realization is must before we claim for licenses (MEIS / RODTEP,etc.)