Refund entitlement for tax and unutilised input tax credit subject to prescribed procedure, documentation and revenue safeguards. Section 54 prescribes claim timelines, eligible categories and exclusions for refund of tax and unutilised input tax credit, requires prescribed documentary proof or a declaration for low-value claims, authorises provisional refunds for zero-rated supplies, and directs the proper officer to make orders within stipulated timeframes. It permits withholding or deduction of refunds where returns are defaulted, amounts remain payable, or where pending proceedings indicate revenue risk, and provides for capped interest if withheld refunds are later adjudged payable.