Stamp Tax Act Article 18
If a taxable document does not indicate a dollar amount, stamp tax shall be determined according to the products and quantity provided in the document and the prevailing market prices of the products at the time of use.
中文原文 印花稅法第18條
應貼印花稅票之憑證，如未載明金額，應按憑證所載品名及數量，依使用時當地時價計貼。