There are no withholding taxes in Hong Kong as such, but there are certain circumstances in which a company making a payment to a foreign associate (subsidiary or holding company) which is deemed to be Hong Kong source income needs to need to withhold the tax.
For instance, when a Hong Kong entity pays royalties for the use of intellectual property to its own offshore licensing affiliate, then tax is due of 10% of 16% = 1.6% and this must be withheld by the Hong Kong paying company.