The one-way permit is actually a colloquial term for the Hong Kong and Macau travel permit.

If a Hong Kong resident has a spouse, children, or other relatives in the mainland who need to go to Hong Kong for support, they can obtain Hong Kong residency through this one-way permit, and after 7 years, they can further obtain permanent residency. However, there is a prerequisite: they must cancel their mainland ID card and household registration, which is why it is called a one-way permit, as it implies 'going without returning'.

Previously, many people from the mainland chose to marry local Hong Kong natives to obtain Hong Kong identity for settlement and employment, using this method. Additionally, the application for the one-way permit is subject to a quota approval system, and the National Immigration Administration announces the approval score line for the following year, scoring and approving applicants based on the scoring criteria.

(1)
Taking family reunification as an example, in 2020, the approval score line for mainland residents settling in Hong Kong and Macau for family reunification was 146.1 points. Each day counts as 0.1 points, starting from the day the marriage certificate is obtained, it takes about 4 years to meet the application conditions. Therefore, couples who started living apart before 2017 can only obtain the one-way permit this year, and this is under the most ideal time conditions. Different provinces have different regulations; for example, in Jiangsu Province, one can apply for the one-way permit and submit materials right after marriage; while in some provinces, one must achieve full points before applying, and in others, one can only apply after three years.

It is recommended that everyone can start applying in the third year after marriage, as the application materials need to be reviewed for completeness and whether the applicant meets the conditions, etc. Even if the score is sufficient, there are still procedures to follow, submitting materials from the city to the province to the Hong Kong verification and then back again. This process generally takes 8-9 months, especially testing the local efficiency.

If there are changes in family status such as divorce or discrepancies in paternity tests during the process, all the waiting will be in vain, as one cannot obtain Hong Kong permanent residency and also loses their mainland identity. Therefore, obtaining Hong Kong permanent residency through the one-way permit carries significant risks.
This is also a question that troubles many friends in the background, why their conditions clearly meet the application for the one-way permit, yet they are always told they are not qualified.
 

(2)

If you really want to obtain Hong Kong identity through family support, it is recommended to choose the dependent visa.

Individuals who obtain Hong Kong identity through the Hong Kong Quality Migrant Scheme can act as sponsors to apply for dependent visas for their spouses and children to also obtain Hong Kong identity, allowing them to settle in Hong Kong or continue living in the mainland.
Once the dependent's application is approved, the Immigration Department will issue an entry permit label, commonly known as the 'pink label'. The duration of stay in Hong Kong is the same as that of the quality migrant, and if they meet the requirement of residing in Hong Kong continuously for 7 years or more, they can also apply to become a permanent resident of Hong Kong.

Changing household registration and identity is not a trivial matter, as it involves various aspects such as buying a house, purchasing a car, children's education, retirement, and medical care.