Refund voucher requirements: specify supplier/recipient IDs, serial/date, linked receipt, refund amount, tax rates, reverse charge and signature. Rule 51 requires a refund voucher to contain supplier and recipient identification (names, addresses, GSTIN or UIN), a unique consecutive serial number for the financial year, date of issue, the related receipt voucher number and date, description of goods or services, amount of refund, applicable tax rates and tax amounts (central, State, integrated, Union territory or cess), indication of reverse charge applicability, and the supplier's signature or digital signature.