You have to post them all. Supply, pre-purchase, procurement, purchase and sale, combination cooperation, adjustment and other contracts. Should be stamped at 0.3‰ of the purchase and sale amount.

Stamp duty is a kind of tax levied on the behavior of signing books and collecting legally effective certificates in economic activities and economic exchanges. It is named after the use of stamping on taxable documents as a tax payment symbol. Taxpayers of stamp duty include enterprises, administrative units, institutions, military units, social organizations, other units, individual industrial and commercial households and other individuals established in China and receiving prescribed economic vouchers.

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Stamp duty related knowledge