This article is written by a Japanese local.
It is quite common for foreign employees relocating from overseas—especially expats and entrepreneurs from Western countries—to hold very generous and comprehensive private medical insurance in their home countries. When they go to the Japanese municipal office (ward office) to register their address or when the company processes their Social Insurance, a specific trouble frequently arises.
They argue: “I already have excellent medical insurance from my home country, and it covers me in Japan too. Therefore, I will not join Japan’s National Health Insurance (or the company’s health insurance). Please exempt me so I don’t have to pay double premiums.”
HR managers must logically and clearly reject this argument. Under the Japanese system, enrolling in public medical insurance is not an “optional choice” but a “strict legal obligation.” This article explains the objective administrative procedures to convince foreign employees of Japanese rules and to guide them on how to correctly use their overseas insurance in tandem with Japan’s public system.
1. The Unbreakable Law of the “Universal Healthcare System”
[Summary] Foreigners residing in Japan for more than 3 months who register as residents are legally mandated to join Japan’s public medical insurance, regardless of whether they hold insurance in their home country.
Japan operates under a “Universal Healthcare System (Kokumin Kaihoken).” This is a mutual aid mechanism where everyone holding a domestic address in Japan pools insurance premiums by joining a public medical insurance program (Social Insurance for corporate employees, or National Health Insurance for others) to support each other’s medical costs.
For foreigners, excluding short-term stays like tourism, the moment they hold a “valid visa with a period of stay exceeding 3 months” and register their address at the municipal office, they fall under the jurisdiction of this law.
Personal circumstances such as “I have my own country’s insurance” or “I won’t go to Japanese hospitals” constitute zero legal grounds to refuse enrollment. Just as a driver cannot say, “I won’t cause accidents, so I won’t buy mandatory auto liability insurance,” HR must objectively communicate that this is a mandatory obligation to participate in Japan’s public infrastructure.
2. The Risks of “Retroactive Billing” and “Visa Renewal Rejection” from Non-Enrollment
[Summary] The obligation does not disappear even if you continue to refuse enrollment. When discovered later, premiums will be billed retroactively in a lump sum back to the date of entry, and visa renewals will be denied.
If an employee ignores the National Health Insurance enrollment procedure at the city office because they “want to avoid paying double,” it may temporarily seem like they have saved money. However, the Japanese administrative system will not overlook this.
The obligation to enroll in National Health Insurance begins on “the day you entered Japan (or the day you lost corporate Social Insurance qualification).” If non-enrollment is discovered a year later and the employee is called to the municipal office, they will be billed for “one full year of past premiums” in a lump sum on the spot.
Even more fatal is the visa renewal process at the Immigration Services Agency. Current immigration screenings strictly check the enrollment status of public medical insurance and the payment records of premiums. If an employee is unenrolled or has arrears, the renewal of their work visa will be “denied,” risking a forced termination of their career in Japan. HR managers must warn them of this severe compliance risk prior to relocation.
3. The “Correct Way to Combine” Japanese Public Insurance and Overseas Private Insurance
[Summary] The most rational approach is to use Japanese insurance to cover 70% of the medical costs, and then claim the remaining 30% “out-of-pocket” expense from the home country’s private insurance.
So, is the private medical insurance the employee is paying for in their home country completely useless? Not at all. By using Japan’s public insurance as the “base” and the overseas insurance as an “optional top-up,” they can reduce their medical burden to virtually zero.
- Step 1: Present the “Japanese Insurance Card” at the Japanese hospital counter
At standard clinics and hospitals in Japan, you cannot receive cashless treatment simply by presenting an overseas insurance card. First, present the Japanese health insurance card and pay the legally mandated “30% co-pay” out-of-pocket at the counter. - Step 2: Receive the Receipt and Medical Certificate
After paying, ask the hospital to issue a “Receipt (Ryoshusho)” and a “Statement of Medical Details,” and if necessary, a “Medical Certificate” (some hospitals can provide this in English). - Step 3: Claim the “30% Co-Pay” from the home country’s insurance company
The employee then submits the documents received from the hospital to their home country’s insurance company to claim a reimbursement for the “30% out-of-pocket expense” they fronted.
This completes a perfect defense mechanism for medical costs: reliable access to treatment through Japanese insurance, and recovery of out-of-pocket expenses through the home country’s insurance.
4. Practical Q&A (Troubleshooting HR Should Guide)
[Summary] Answers questions regarding exceptions under Social Security Agreements (bilateral treaties) and the difference from travel insurance.
Q. I heard that employees from countries with a “Social Security Agreement” with Japan are exempt from Japanese health insurance. Is this true?
A. Japan has “Social Security Agreements” with multiple countries to prevent double payments. However, most of these agreements focus on preventing double enrollment in “Pensions.” Countries where “Medical Insurance (Health Insurance)” is also exempt are very limited (e.g., the US, France, Germany, under strict conditions such as the expected assignment period being 5 years or less). To apply for this exemption, a complex procedure is required, including submitting a “Certificate of Coverage” issued by the home country’s government agency to the Japanese Pension Office. Without this certificate, enrollment in Japanese insurance remains a strict obligation.
Q. Isn’t the “Overseas Travel Insurance” attached to my credit card sufficient?
A. It is completely insufficient. Overseas travel insurance and credit card supplemental insurance are strictly emergency insurances based on the premise of a “short-term stay (travel) of 90 days or less.” In most cases, “mid-to-long-term residents with an address in Japan (visas exceeding 3 months)” are excluded from coverage entirely. Furthermore, they do not cover treatments for chronic diseases, dental care, or pregnancy/childbirth. Instruct employees that these cannot substitute for Japan’s public infrastructure.
Conclusion: Participating in Public Infrastructure is the “Ticket to Work in Japan”
The logic of “I won’t join because I have better insurance of my own” might fly in contract-based societies overseas, but it is entirely unacceptable under Japan’s legal system, which is premised on mutual aid. During pre-relocation orientations, HR managers must firmly persuade employees from an objective compliance perspective: “Enrolling in Japan’s public medical insurance is the absolute ticket to maintaining your work visa and living safely in Japan.”