Act Governing Relations with Hong Kong and Macau Article 29

A Hong Kong or Macau Resident who has income from sources in the Taiwan Area shall pay income tax on said income in accordance with provisions of the Income Tax Law.The income of Hong Kong or Macau juridical persons, organizations or other institutions from sources in the Taiwan Area shall be taxed in accordance with the provisions of the Income Tax Law governing profit-seeking enterprises headquartered outside the territory of the Republic of China.
中文原文 香港澳門關係條例第29條
香港或澳門居民有臺灣地區來源所得者,應就其臺灣地區來源所得,依所得稅法規定課徵所得稅。
香港或澳門法人、團體或其他機構有臺灣地區來源所得者,應就其臺灣地區來源所得比照總機構在中華民國境外之營利事業,依所得稅法規定課徵所得稅。

English translation for reference only; the Chinese text prevails. Not legal advice.