The principle of unjust enrichment would be applicable in all cases of refund except in the following cases:-
1. Refund of tax paid on zero-rated supplies of goods or services or both or on inputs or input services used in making such zero-rated supplies
2. Unutilized input tax credit in respect of (i) zero-rated supplies made without payment of tax or, (ii) where the credit has accumulated on account of the rate of tax on inputs being higher than the rate of tax on output supplies
3. Refund of tax paid on a supply which is not provided, either wholly or partially, and for which invoice has not been issued;
4. Refund of tax in pursuance of Section 77 of CGST/SGST Act i.e. tax wrongfully collected and paid to Central Government or State Government
5. If the incidence of tax or interest paid has not been passed on to any other person;
6. Such other class of persons who have borne the incidence of tax as the Government may notify.