According to the query of Baidu Library, the enterprise service trade tax filing must upload the contract. In the process of contract filing, the contract number given by the system cannot be modified by itself, and it should be remembered that when withholding tax, you should declare and apply for payment under this contract number, otherwise it will easily lead to subsequent management warning. Therefore, enterprises must upload relevant contracts when filing service trade tax returns.

Tax filing refers to tax registration, which is a legal system for tax authorities to register and manage taxpayers' production and business activities according to the provisions of the tax law, and also a legal procedure for taxpayers to fulfill their tax obligations according to law.