You have joined your employer’s health insurance, but National Health Insurance (国民健康保険, or kokumin kenkō hoken) payment slips are still arriving. Joining a workplace plan does not automatically cancel your municipal National Health Insurance enrollment. Notify the municipality where you are enrolled, using proof of the new plan’s effective date. Then check the revised premium notice rather than guessing which remaining slips to pay.
Japanese terms you will see
| Japanese | Reading | English meaning |
|---|---|---|
| 国民健康保険 / 国保 | kokumin kenkō hoken / kokuho | Municipal National Health Insurance / its abbreviation |
| 職場の健康保険 | shokuba no kenkō hoken | Health insurance through your workplace |
| 資格取得日 | shikaku shutoku-bi | Date your new coverage began |
| 資格喪失 / 脱退 | shikaku sōshitsu / dattai | Loss of National Health Insurance eligibility / withdrawal |
| 資格確認書 | shikaku kakunin-sho | Document confirming health insurance eligibility |
| 資格情報のお知らせ | shikaku jōhō no oshirase | Notice of insurance eligibility information |
| 健康保険資格取得証明書 | kenkō hoken shikaku shutoku shōmeisho | Certificate showing acquisition of workplace health insurance |
| 保険料変更通知書 / 還付 | hokenryō henkō tsūchi-sho / kanpu | Revised premium notice / refund |
What to do after your workplace coverage starts
- Confirm the effective date and everyone covered. Ask your employer for proof of the 資格取得日 for you and any family members who also left the municipal plan. A job offer date or first paycheck date is not necessarily the insurance effective date.
- Look up your municipality’s 国民健康保険 脱退 procedure. Check its deadline, who may submit the notice, accepted proof and whether it allows counter, postal, or online submission. Yokohama City asks residents to report the change within 14 days and offers in-person, postal and online routes. Your municipality’s current instructions control your application.
- Prepare proof of the new plan. Yokohama lists a qualification confirmation document, qualification information notice, certificate from the employer or insurer, or My Number card plus the relevant Mynaportal eligibility screen as examples that establish the effective date. Bring or submit documentation for each person leaving National Health Insurance, the old qualification confirmation document if held, and the applicant’s identity document as required locally. Its postal instructions specify the copies and form for that route.
- Submit and retain a record. Keep a copy, receipt, confirmation email or reference number. If the new insurance information has not appeared in Mynaportal yet, ask your employer or municipal office which alternative proof is accepted. Online eligibility and document rules vary: Shinjuku’s online procedure, for instance, excludes some moves and proxy applications.
- Check the later premium adjustment. If a new notice arrives, compare the covered months and revised amount. Yokohama cautions that the month a premium is charged or paid can differ from the months used to calculate it, so slips may still be issued for later installments or a refund may follow. Shinjuku advises using the latest payment slips after a midyear change. Ask the insurance counter before discarding or withholding payment on a slip you do not understand.
Useful questions in Japanese
| Japanese | Reading | Meaning |
|---|---|---|
| 職場の健康保険に加入したので、国民健康保険の脱退手続きをしたいです。 | Shokuba no kenkō hoken ni kanyū shita node, kokumin kenkō hoken no dattai tetsuzuki o shitai desu. | I joined workplace health insurance and would like to withdraw from National Health Insurance. |
| 資格取得日が分かる書類は、これで大丈夫ですか。 | Shikaku shutoku-bi ga wakaru shorui wa, kore de daijōbu desu ka. | Is this document sufficient to show the effective date? |
| 家族も一緒に脱退する場合、何が必要ですか。 | Kazoku mo issho ni dattai suru baai, nani ga hitsuyō desu ka. | What is needed if my family is leaving the plan too? |
| この納付書は、手続き後も支払う必要がありますか。 | Kono nōfu-sho wa, tetsuzuki-go mo shiharau hitsuyō ga arimasu ka. | Do I still need to pay this slip after the procedure? |
Two easy mistakes to avoid
Using the old coverage after the new plan begins: Ask the medical provider and your insurers which coverage applies to a visit around the changeover. Yokohama says that using its National Health Insurance after joining another plan can lead to a request to repay the city’s share of medical costs.
Assuming payroll handles the municipal notice: Your employer arranges the workplace plan, but the municipal withdrawal remains a separate procedure. Shibuya explicitly warns that joining another plan does not automatically end National Health Insurance. For help reading the revised bill, use our National Health Insurance payment notice guide. If this change followed a move, the address-change checklist covers the separate residence procedures.
