Unjust enrichment bars supplier refunds unless the claimant proves the tax burden was not passed on to others. The principle of unjust enrichment prevents refunds from enriching a supplier who passed the tax burden to recipients; refunds are generally credited to the Consumer Welfare Fund and will be paid directly to claimants only where the claimant shows the tax incidence was not passed on. The proper officer must satisfy this condition except in specified categories where the unjust enrichment doctrine does not apply, such as certain export-related refunds, unutilised input tax credit, supplies not provided, tax wrongfully collected, and cases where the applicant did not pass on the tax burden.