Is it tax-related to pay the design fees of Hong Kong companies?

Tax related. If you pay the design fee of a Hong Kong company, you need to pay the relevant taxes in accordance with the relevant tax laws. According to the Individual Income Tax Law of People's Republic of China (PRC), the income from labor remuneration and authorized rights and interests paid by domestic units or individuals to overseas individuals or units shall be withheld and remitted in accordance with the provisions of the tax law. The specific tax rate and calculation method may be different according to the situation. I suggest you consult a professional tax agency or law firm to get a more accurate and reliable answer. At the same time, when making cross-border payments, it is also necessary to pay attention to abide by relevant laws, regulations and policies to ensure that transactions are legal and compliant.