Stamp Tax Act Article 13

If the same document can be categorized under two types of document subject to the same tax rate, only tax stamps applicable to one type of document are required; if the same document is subject to different tax rates, the higher rate shall govern. Where a document subject to a higher tax rate is substituted by a document subject to a lower tax rate, the document shall be affixed with tax stamps in the amount calculated at the higher tax rate. Where a taxable document is substituted by a tax-exempt document, tax stamps corresponding to the type of the taxable document shall be affixed.