Signing Up for National Health Insurance (国民健康保険)

You have to enrol — even if you have other insurance

Japan has universal coverage: every resident must belong to a public health plan. If you work for a company, your employer puts you on its 健康保険kenkō hoken and there’s nothing to do at city hall. Everyone else — the self-employed, freelancers, students, the not-yet-employed — enrols in 国民健康保険kokumin kenkō hoken (National Health Insurance) at the municipal office.

The part that surprises new arrivals from the US: enrolment is mandatory, and holding private or foreign insurance does not get you out of it. The only people exempt from National Health Insurance are those already on Japanese employer 健康保険kenkō hoken, those in the 後期高齢者医療制度kōki kōreisha iryō seido (the system for ages 75+), and those on public assistance. A US or international plan — a Cigna policy, an employer’s global plan, retiree coverage — is not on that list. You enrol regardless, and treat the foreign plan as something extra (more on that below).

The mechanics of enrolling are part of your first city-hall visit — see Registering at City Hall.

What it costs, and what you carry

• Premiums are set by your municipality, based mainly on your prior year’s income — so a newcomer’s first-year premium is often low (little or no prior Japanese income), then rises. They’re billed by the city.
• At the clinic you pay about 30% of the cost, and the insurer covers the rest. The share is lower for some ages — 20% for pre-school children and for ages 70–74, and 10% at 75+ (higher for high earners).
• Coverage back-dates to your registration date, so don’t delay enrolling.
• What you show at the desk is no longer a paper card: Japan retired the old 健康保険証kenkō hokenshō, so you use a マイナ保険証maina hokenshō (your My Number Card registered as your insurance card) or a free 資格確認書shikaku kakuninsho.

The cap that changes the math: 高額療養費

This is the single most important thing to understand before deciding whether you need extra insurance. The 高額療養費kōgaku ryōyōhi (High-Cost Medical Expense Benefit) puts a monthly ceiling on your out-of-pocket for covered care, scaled to your income; anything above the ceiling is reimbursed. For a typical working-age earner that ceiling lands in the order of ¥80,000–90,000 in a heavy month, not a percentage of a frightening total — so even a major hospitalization is bounded.

Two caveats: the ceiling is income-based (higher earners pay more, lower earners less) and is revised periodically — a revision is scheduled for 2026 — so treat any figure as approximate. And the cap covers insured costs only; the extras below sit outside it.

What public insurance doesn’t cover

These are the gaps — and the reason supplemental insurance exists:

• 差額ベッド代sagaku beddo-dai — the surcharge for a private or small-shared hospital room, when you choose one.
• 先進医療senshin iryō — designated advanced treatments not yet covered; the ordinary parts of your care stay insured, but the advanced portion is paid in full and can be very expensive.
• Elective and cosmetic care, and fully private (out-of-pocket) treatment.
• Normal childbirth, which isn’t classed as “treatment” — instead you receive the 出産育児一時金shussan ikuji ichijikin lump sum (currently ¥500,000 per child). (Whether normal birth should be insured is under review.)
• Income while you can’t work: employer 健康保険kenkō hoken pays a sickness allowance (傷病手当金shōbyō teate-kin), but National Health Insurance has no equivalent — a real gap for the self-employed.

Optional supplemental (private) insurance

Private insurers sell cover that tops up the public system — 民間医療保険minkan iryō hoken (daily hospitalization cash, surgery benefits, riders), がん保険gan hoken (cancer), and income-protection policies. They’re genuinely optional: because 高額療養費kōgaku ryōyōhi already caps catastrophic cost, the practical question is narrower than it looks — whether you want to cover specific gaps like private rooms, 先進医療senshin iryō, or lost income if you’re self-employed.

One important US-person caution. A plain protection policy — term medical or cancer cover with no savings element — is straightforward. But a Japanese policy with a cash or investment value (endowment, whole-life, “unit-linked” savings insurance) can create real US problems: its cash value is reportable on your FBAR and Form 8938, an investment-type policy can fall under PFIC treatment (see Investing from Japan as a US Person), and the US even levies an excise tax on premiums paid to foreign insurers. Get cross-border tax advice before buying anything with a savings component; stick to pure protection if you want to keep it simple.

If you have US-based insurance (Cigna, employer plans, Medicare)

Plenty of US persons arrive already insured. Here’s how that fits:

• It doesn’t replace National Health Insurance. As above, you still enrol — the foreign plan is supplemental, not a substitute.
• US domestic plans usually don’t cover routine care in Japan. A standard stateside plan treats Japan as out-of-network or simply doesn’t cover overseas care (some cover emergencies only) — check your policy before relying on it.
• International/expat plans (e.g., Cigna Global, an employer’s global medical plan) do cover Japan, but typically on a reimbursement basis — Japanese clinics bill you directly, not your foreign insurer, so you pay and claim back. Their real value is often the extras: worldwide cover for travel and US trips, choice of provider, and medical evacuation/repatriation. A common setup is National Health Insurance as your primary coverage in Japan, with an international plan layered on top.
• Medicare does not cover care in Japan (only very narrow exceptions). This matters most for retirees: you can’t rely on Medicare here — National Health Insurance, then the 後期高齢者医療制度kōki kōreisha iryō seido at 75, is your coverage. Whether to keep paying Medicare Part B premiums to preserve it for US visits is a personal cost-benefit call.
• SOFA status is different: SOFA-status personnel and families use the US military health system and are outside National Health Insurance entirely — see SOFA Status in Japan.

If you do keep a US or international plan, treat National Health Insurance as primary for care in Japan and your foreign plan as the backstop — and keep your itemized Japanese receipts, since reimbursement claims need them.

The short version

• If you’re not on an employer’s 健康保険kenkō hoken, enrol in 国民健康保険kokumin kenkō hoken at city hall — mandatory, and a US/Cigna plan doesn’t exempt you.
• You pay about 30% at the clinic, and 高額療養費kōgaku ryōyōhi caps your monthly out-of-pocket — so catastrophic cost is bounded.
• Public insurance skips private rooms (差額ベッド代sagaku beddo-dai), 先進医療senshin iryō, elective care, and income replacement — the gaps supplemental insurance fills.
• Supplemental cover is optional; pure protection is fine, but cash-value Japanese policies carry US tax/reporting complications.
• Medicare won’t cover you in Japan; international plans (Cigna Global, etc.) reimburse after you pay — keep National Health Insurance as primary.

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This guide is general information, not tax, insurance, or medical advice. Premiums, cost-sharing, the 高額療養費kōgaku ryōyōhi ceilings, and coverage rules vary by municipality and income and change over time (some are being revised in 2026) — verify against the official sources below and your city office, and bring insurance and cross-border tax questions to qualified professionals.