Double taxation is generally defined as the imposition of comparable taxes in two or more places on the same taxpayer in respect of the same subject matter and for identical periods. Hong Kong adopts a Territorial Source Principle of Taxation, which means only profits which arose in, or are derived from, Hong Kong are taxable in Hong Kong. This means that profits generated from overseas are not taxable in Hong Kong, but are most probably still taxable in the country where the profits originated from.
For individuals who work in a different country but resides in Hong Kong, depending upon different countries' laws, may be required to pay income tax from both countries. The function of Double Tax Avoidance ("DTA") resolves the issue that the individual will only be taxed based on its residency.
For an entity / corporation, profits derived from activities involving the two countries will only be taxed by one country, or, in the case of apportionment, profits derived from one country will be taxed by that country under the DTA.