Zero rated supply refund formula clarified, with procedural limits on registration amendments and revised forms for nonresident suppliers. Amendments deem the Central GST Unique Identity Number to apply under the Tamil Nadu Act, restrict retrospective amendment of registration particulars absent Commissioner's order, and substitute rule 89 to prescribe a formula for refund of input tax credit on zero-rated supplies linked to turnover of zero-rated goods and services, net ITC and adjusted total turnover, including definitions and sub-rules (4A)/(4B) specifying refund eligibility where suppliers have availed specified notifications. Procedural changes mandate quarterly FORM GST RFD-10 filing with GSTR-11, expand rule 96 to include services and disqualify certain refund claimants, and substitute multiple registration and refund forms.