Bill of supply requirements specify mandatory invoice elements and treat equivalent non taxable documents as bills of supply. A bill of supply must include the supplier's name, address and GSTIN; a unique consecutive serial number (permitted characters include letters, numerals, '-' and '/'); date of issue; recipient's name, address and GSTIN or UIN if registered; HSN code or accounting code; description of goods or services; value of supply after discounts or abatements; and the supplier's signature or digital signature. Provisos to related invoice rules apply mutatis mutandis, and any similar document for a non taxable supply under other law is deemed a bill of supply.