Under the health insurance, insurance benefits are paid not only to the insured person, but also to family members who are dependent on the insured person. These family members are called "dependents," and the family members who may become dependents are defined by law.
*In principle, only residents of Japan are eligible (from April 1, 2020).

Scope of qualifications as a dependent

To qualify as a dependent of an insured person, an individual must depend for his or her living primarily on the income of the insured person.
Specifically, in order to meet this standard the person wishing to become a dependent must have an annual income (i.e., total income including benefits received from sources such as unemployment insurance and pensions) less than the following base levels “(1)” and “(2)”:

(1) When the prospective dependent lives with the insured person:
The person wishing to become a dependent must earn less than 1.3 million yen per year (or less than 1.8 million yen per year if he or she is aged 60 or over or is handicapped), and his or her annual income must total less than half of the insured person's income.

(2) When the prospective dependent does not live with the insured person:
The person wishing to become a dependent must earn less than 1.3 million yen per year (or less than 1.8 million yen per year if he or she is aged 60 or over or is handicapped), and his or her annual income must total less than the amount of funds sent to him or her by the insured person.

However, since those aged 75 and above are covered under the medical system for persons in the latter stages of old age, they are not eligible to become dependents under the health insurance system.

● Government measures to address annual income barriers (starting in October 2023)

(Reference link)
・Support enhancement package for overcoming annual income barriers (Ministry of Health, Labour and Welfare)

■ What are annual income barriers?

Annual income barriers refer to threshold income amounts that determine whether or not taxes and social insurance premiums are incurred.
Individuals who have dependent status and work part-time or other non-regular jobs will lose their dependent status if their annual income exceeds a certain figure, and become an insured person under a company health insurance plan, National Health Insurance, or other insurance system. They will then be required to pay social insurance premiums, which may result in lower take-home pay.
One of two different annual income barriers applies for social insurance premiums, depending on company size and other factors: 1.06 million yen or 1.3 million yen.

(Source: Provisional measures to address annual income barriers (Ministry of Health, Labour and Welfare))

■ Handling for the 1.3 million yen annual income barrier

Although dependent certification is based on checking of taxation certificates and other documents from the previous year, if the worker’s annual income is expected to temporarily exceed 1.3 million yen due to longer hours because of labor shortage or other factors, the worker may choose to retain his or her dependent status simply by attaching a certificate from the employer.
(In principle, this handling is available no more than two consecutive times for a single worker.)

■ Handling for the 1.06 million yen annual income barrier

Companies that help increase worker income through means such as payment of allowances to encourage social insurance coverage* will be provided subsidies for a finite term.

* Allowances to encourage social insurance coverage

These allowances are intended to encourage employee insurance coverage for those working reduced hours and to reduce the burden of insurance premiums when workers who had been ineligible for insurance are newly covered by insurance.
Allowances to encourage social insurance coverage are to be paid apart from salaries and bonuses. They are not considered when calculating the standard monthly remuneration or standard bonuses used to determine insurance premiums.

* Eligible persons: Those with standard monthly remuneration of 104,000 yen or less

* Maximum allowance amount excluded from standard remuneration: Amount equivalent to the insurance premiums newly incurred by the employee due to insurance coverage

* A time-limited measure not to exceed two years

New requirement concerning residency in Japan for dependent certification

From April 2020, a requirement related to residency in Japan is added to the requirements for certification of health insurance dependents. In principle, from April 1, 2020, those who do not have addresses in Japan cannot be certified as dependents (with certain exceptions - for example, students studying abroad).

Rationale underlying the domestic residency requirement

Determinations of residency are based on whether a person is registered to the basic resident register (i.e., whether or not the person has a certificate of residence). In principle, those who have certificates of residence in Japan meet the domestic residency requirement.

Note: Even those who have certificates of residence in Japan will not satisfy the domestic residency requirement if they clearly do not reside in Japan - for example, those employed overseas.

Exceptions to the domestic residency requirement

Those whose livelihoods are recognized to be based in Japan, such as students studying abroad temporarily, are considered to meet the domestic residency requirement on an exceptional basis, even if they actually reside overseas.

[Cases qualifying as exceptions to the domestic residency requirement]

(1) Students studying abroad

(2) Family members accompanying an insured person posted abroad

(3) Those traveling abroad temporarily for sightseeing, recreation, volunteer activities, or other reasons unrelated to employment

(4) Those who enter into a family relationship to an insured person while the insured person is posted abroad

(5) In addition to those described under (1)-(4) above, others whose livelihoods are recognized to be based in Japan in consideration of purposes of traveling abroad and other circumstances

Cases in which a person cannot be certified as a dependent even if he or she resides in Japan

Those who come to Japan on medical visas or on long-stay visas for sightseeing or recreational purposes cannot be certified as dependents, even if they reside in Japan.

Interim measure

As an interim measure, if a person who would lose his or her eligibility as a dependent due to the addition of the domestic residency requirement is hospitalized in a medical care institution in Japan as of the date of enactment of the requirement (April 1, 2020), his or her eligibility will continue during the period of hospitalization.

When a change occurs in information for dependents

When a family member once authorized as a dependent no longer satisfies the criteria due to employment, separation, or death, procedures are required to remove him or her from the list of dependents.
Procedures are also required to remove a dependent who has turned 75 from the list of dependents.
See here for details. >> "When someone is no longer a dependent"