日本語版はこちら / Japanese version → 国民健康保険とは？外国人の入り方・保険料・使い方
If you live in Japan for more than three months, you must join National Health Insurance (国民健康保険 / kokumin kenkō hoken), usually shortened to kokuho (国保).
This is not optional. It is a legal requirement. But it is also one of the best things about living in Japan: it turns a ¥10,000 hospital bill into a ¥3,000 bill.
This guide explains how to join, what it costs, and the mistakes that cause real problems — including one that can affect your visa renewal.
- Why this matters: you pay only 30%
- Who must join
- Join within 14 days — this is important
- Where to go and what to bring
- What it costs
- If you cannot afford it, do not ignore it
- Using your insurance card
- If your bill is very large: the high-cost medical system
- Things people get wrong
- Quick summary
- Related guides
Why this matters: you pay only 30%
With kokuho, the government pays 70% of your medical costs. You pay the remaining 30%.
The same 30% rate applies to a ¥50,000 surgery — you would pay ¥15,000. It works at hospitals, clinics, pharmacies, and dentists. (Cosmetic treatment such as teeth whitening is not covered.)
Who must join
- Anyone staying in Japan more than 3 months
- Anyone not covered by an employer’s health insurance (社会保険 / shakai hoken)
If your company enrolls you in shakai hoken, you do not join kokuho. You are in one system or the other, never both. Most students and many part-time workers are in kokuho.
Join within 14 days — this is important
You must apply within 14 days of registering your address at the city office.
Why this matters: coverage does not start from the day you apply. It starts from the day you became a resident. So if you delay:
- You will be charged the back premiums for all the months you skipped
- Any hospital visit before you joined is 100% your cost, and cannot be refunded later
Example: you arrive on 1 April but join in May. Your April hospital bill stays 100% yours — and you still owe April’s premium.
Where to go and what to bring
Go to the city, ward, or town office (市役所・区役所・町役場) for the address where you actually live. You cannot do this at a different municipality’s office.
At the office, look for one of these counters:
- 国民健康保険課 (kokumin kenkō hoken ka) — National Health Insurance Division
- 保険年金課 (hoken nenkin ka) — Insurance and Pension Division
You can show that text on your phone at the information desk.
Bring these
- Residence card (在留カード / zairyū kādo) — essential
- Passport
- My Number card or notification slip (マイナンバーカード / 通知カード)
- Personal seal (印鑑 / inkan) — many offices now accept a signature instead
- Student ID (学生証) — sometimes requested
Requirements vary slightly by municipality, so check your city’s website first if you can. If you have already registered your address, see our guide to the residence certificate (juminhyo).
What it costs
Premiums are not the same everywhere. Each municipality sets its own rate, and the amount is based on last year’s income.
Because most students earned little or nothing in Japan last year, their premiums are usually low:
- Students with little income: roughly ¥1,000–2,000 per month
- Those working more part-time hours: roughly ¥3,000–5,000 per month
Your city office can tell you your exact amount. If you work part-time, our guide on tax for part-time workers explains how income is counted.
How to pay
- Payment slip (納付書 / nōfusho) at a convenience store or bank
- Automatic bank transfer (口座振替 / kōza furikae) — easiest, set it up once
Monthly is standard, but you can pay several months at once.
If you cannot afford it, do not ignore it
This is the most important paragraph in this article.
If you stop paying:
- Your insurance card can stop working — you pay 100% at the hospital
- Late fees (延滞金 / entaikin) are added
- It can affect your visa renewal. Immigration may check whether you have paid. Unpaid premiums can be treated as a sign that you are not meeting your obligations as a resident.
That last point surprises many people, and it is the reason ignoring the bills is dangerous.
Go to the city office and say you cannot pay. Reduction programmes (減免 / genmen) and instalment plans exist, and low-income residents often qualify. Staff will not report you or cancel your visa — their job is to arrange payment. Asking early is always cheaper than staying silent.
Using your insurance card
After you join, you receive an insurance card (保険証 / hokenshō). Carry it in your wallet at all times.
- Show the card at the hospital reception
- Give your name and date of birth
- Pay only your 30% at the end
- At the pharmacy, show the card again to get medicine at 30%
If you forget your card
You pay 100% that day. Keep the receipt, take it to the city office, and you can claim the 70% back. You do not lose the money — it just takes extra work.
Card rules
- Update your address immediately if you move
- Check the expiry date and renew on time
- Never lend your card to anyone. This is a crime in Japan, and it can end your stay.
If your bill is very large: the high-cost medical system
If you need surgery or a hospital stay, costs can be high even at 30%. Japan has a safety net called the High-Cost Medical Expense Benefit (高額療養費制度 / kōgaku ryōyōhi seido).
It sets a monthly maximum based on your age and income. Anything above that limit is refunded. For a low-income resident, the ceiling is often only a few tens of thousands of yen for the whole month.
At the hospital counter, say: 「高額療養費制度について教えてください」 (“Please tell me about the high-cost medical expense system”). Ask before a planned hospital stay if possible — it is easier to apply in advance than to claim back later.
Things people get wrong
Going home for the holidays
Your Japanese insurance card does not work overseas. If you get treated in Nepal or Sri Lanka, you pay in full there. In some cases you can claim part of it back after returning to Japan — keep every receipt and ask your city office.
Also note: you still owe premiums while you are away, because you are still a registered resident of Japan.
Being sent to the wrong kind of hospital
For everyday problems — a cold, a fever, an injury — go to a small local clinic (クリニック / 医院), not a large hospital. Clinics have shorter waits. If you need more, they will refer you to a hospital.
Accepting treatment that insurance does not cover
Some treatment is “free treatment” (自由診療 / jiyū shinryō) and is not covered at all. If you do not understand what is being proposed, ask: 「これは保険が使えますか？」 (“Is this covered by insurance?”) before agreeing.
Quick summary
- Staying over 3 months and not on company insurance → you must join
- Apply at your city office within 14 days
- Bring your residence card, passport, and My Number
- You then pay only 30% of medical costs
- Cannot pay? Ask about genmen — never just ignore it
- Unpaid premiums can affect your visa renewal
Related guides
- How to get your residence certificate (juminhyo)
- Tax rules if you work part-time
- How renting an apartment works in Japan
- Sending money home from Japan
If this helped, please share it with a friend who has just arrived. Most people learn these rules only after they have already lost money.
