It has nothing to do with the contract. The key depends on whether to export, obtain the customs declaration form and the foreign exchange verification form and the tax refund form. If you are a foreign trade enterprise, you must have a special invoice for the domestic purchase of exported goods, but first you must apply for a general taxpayer, because small-scale taxpayers are tax-free, and you can check whether the exported goods belong to non-refundable goods on the website of State Taxation Administration of The People's Republic of China.