SAD 4% REFUND

if the seller is not paying the vat then he can not claim refund for SAD. because the basic condition is that claim is available if you have paid the VAT OR CST to the authorities. while issuance of certificate of SAD the statutory auditor should counter check the all challan of  tax paid to authorities.

in the given case as far as i think the claim is not available because tax has not been deposited.

you can place claim for refund to customs subject to submission of proof of actual payment of VAT against sales of imported goods, 

in absence of such proof, the claim is inadmissible.