This belongs to the taxable income obtained by Hong Kong companies in Chinese mainland, and your company has the obligation to withhold and remit it.

Declare to the local tax authorities respectively, and the business tax is 5% according to the service tax item; Non-resident enterprise income tax is declared to the State Administration of Taxation, with the tax rate of 10%, and the base is full income.

2. If the amount exceeds US$ 30,000, the local tax authorities must also issue foreign exchange payment vouchers for service trade payment.

3. After the payment, your company should obtain the invoice or similar evidence from the Hong Kong company as the basis for the pre-tax payment of enterprise income tax.

Please consult the local tax authorities for specific procedures.

PS:

1. Although the Mainland and Hong Kong are one country, their tax systems are different. Hong Kong has a separate tax system, so Chinese mainland and Hong Kong have signed tax arrangements (because Hong Kong belongs to China, it is called tax arrangements, and China has signed agreements with other countries). If he wants to enjoy the tax arrangement, it means that he has to pay enterprise income tax in Hong Kong, not in the mainland, and he can wait for the tax payment certificate of Hong Kong residents.

This tax is paid by a Hong Kong company and has nothing to do with you. You can deduct as much as he should pay, and you can tell him that it was paid by the tax bureau.