Refund voucher requirements: specify supplier and recipient details, refund amount, tax particulars, serial number and signature. A refund voucher must identify supplier and recipient with GSTIN or UIN where applicable, include date of issue and related receipt voucher number and date, describe the goods or services, state the refund amount, and present tax particulars including tax heads, rate, amount paid and whether reverse charge applies; it must bear a consecutive serial number unique for the financial year and the supplier's signature or digital signature.