I understand there are three categories: Mainland Tax Residents (Retaining Mainland Household Registration / Residing in Hong Kong for at least 183 days annually) Regardless of whether they are in Hong Kong or not, all global income must be declared to the Mainland. Transaction gains are taxed at 20% as "income from property transfer." Hong Kong Tax Residents No Capital Gains Tax: Long-term investments, occasional transactions → considered capital gains, not taxed in Hong Kong. High-frequency, systematic, using robots/teams/leverage/short holdings → considered "business operations," taxed as profits: Individual/Unlawful Organization Business: Approximately 15%. Company Form: 8.25% for the first HKD 2 million, 16.5% for the excess. Of course, the Mainland doesn't currently regulate this area, similar to trusts. It should be gradually implemented in the future; retrospective investigation is just a matter of time. However, the Mainland has not yet joined CARF, so the latest exchange information will not be exchanged for the time being. The main focus is on CRS, i.e., bank deposit and withdrawal information. But the information of these exchanges before these business owners left the Mainland has definitely been fully integrated with the Mainland government.