Kyokai Kenpo vs a Health Insurance Society: What Differs

The short answer: the two differences are how the rate is set and the employer's share

Sources: Kyokai Kenpo[Kyokai Kenpo], Kenporen[Kenporen], Health Insurance Act[Health Insurance Act]

Statutory benefits and the statutory range for the rate are the same on both sides.

The rate is set by prefecture or by society - from 9.21% in Niigata to 10.55% in Saga

Kyokai Kenpo rates differ by prefecture, and the FY2026 rates took effect from the March premium (paid in April)[Kyokai Kenpo]. The national average fell 0.1 points from 10.00% the previous year to 9.90%[Kyokai Kenpo].

Source: Kyokai Kenpo (health insurance rate only)[Kyokai Kenpo]

The gap between Saga and Niigata is 1.34 points. On the same salary, the prefecture your employer sits in changes your own share by about ¥29,000 a year. That is a gap nothing you do at work can close.

The range for a society's rate is also set by law. Article 160 of the Health Insurance Act sets it at "30 to 130 per thousand", that is 3% to 13%, and paragraph 13 of the same article applies that to societies[Health Insurance Act, Article 160]. The 13% ceiling is not something that applies to societies alone. Their rates are spread out like this[Kenporen].

• The largest band is 9.5% to under 10.0%, with 401 societies (29.4%)
• 92 societies are under 8.0%, and 25 are at 11.0% or above

There are also 376 societies (27.6%) at or above the Kyokai Kenpo average of 9.90%. The published bands stop at "11.0% or above", so we cannot tell whether any society has gone as far as 13%.

The real reason large companies have cheap health insurance is the employer's share

What reaches your take-home pay is the employer's share rather than the rate. Article 161 of the Health Insurance Act has the employee and the employer each pay half. Article 162 lets societies, and only societies, raise the employer's share in their own rules[Health Insurance Act, Articles 161 and 162]. Kyokai Kenpo has no such exception, so it is always an even split.

Note: the society's 9.00% and the employer's 60% are illustrative figures. They are not a worked example published by any public body.

A society with a rate 0.85 points lower still only saves you ¥18,360 a year. At the same rate, an employer paying 60% saves you ¥57,240 a year - three times as much.

The catch is that the split is set in the society's own rules, and it is hard to find out from outside before you join. Nor is the share of societies that go above half published anywhere. Once you are in, you can tell by comparing your payslip with the standard monthly remuneration times the rate divided by two. There is a rough guide in the social insurance premium table by monthly salary.

The societies' average of 9.32% is cheapness paid for by deficits

The societies' average rate of 9.32% is below Kyokai Kenpo's 9.90%. But Kenporen itself puts the effective rate needed to balance the books at 9.90%[Kenporen]. Today's cheapness is cheapness held up by deficits.

The FY2026 budgets show an ordinary deficit of ¥289 billion, and 1,010 of the 1,364 societies, about seven in ten, are in the red[Kenporen]. Kenporen writes that the fall in rates is temporary and that increases cannot be avoided. The reason is that contributions to elderly medical care are rising from 40% of premium income towards about 50%.

When a society is wound up, its members move to Kyokai Kenpo, because Article 26(4) of the Health Insurance Act has the Association succeed to its rights and obligations[Health Insurance Act, Article 26]. The number of societies fell from 1,372 to 1,364, but that is a net figure that includes mergers, and the number of windings-up is not published.

Statutory benefits are the same; only societies add supplementary benefits

The 30% co-payment at the counter, the high-cost medical expense benefit, the sickness allowance and the maternity allowance are the same on both sides. What differs is supplementary benefits. Article 53 of the Health Insurance Act is headed, in so many words, "Supplementary benefits of health insurance societies", and allows the top-up to societies only[Health Insurance Act, Article 53].

Note: our own estimate for someone with a standard monthly remuneration of ¥360,000 spending a month in hospital. The cap is ¥85,800 plus 1% of (medical costs minus ¥286,000)[MHLW]. The caps come from each society's own explanation[Tokyo Information Service Industry HIS][Fujitsu HIS]. Extra charges for a private room are excluded.

For the same illness and the same treatment, what you pay differs by ¥72,900. Supplementary benefits across all societies come to ¥119.7 billion, only 2.3% of their statutory benefit spending[Kenporen]. Small for the system as a whole, but large for the person who uses it.

Note, though, that supplementary benefits are counted per claim form. Visit a hospital, a pharmacy and a dentist in the same month and the cap applies to each of them[Fujitsu HIS]. How to look yours up is in supplementary benefits of health insurance societies.

Long-term care rates and health promotion spending differ too

People aged 40 to 64 also have long-term care premiums deducted. Kyokai Kenpo charges a single national rate of 1.62%; societies each set their own, and the FY2026 average is 1.70%[Kenporen]. A society with a low health insurance rate can still have a high long-term care rate. The child and childcare support levy of 0.23% is the same nationwide, and Kyokai Kenpo adds it from the April 2026 premium[Kyokai Kenpo].

What the money goes on beyond benefits differs as well. Societies spend ¥490.6 billion on health promotion, ¥28,657 per insured person a year[Kenporen]. That is what pays for extra health checks and holiday facilities (the per-person figure is our own estimate).

The dependency test is the same; the paperwork asked for is not

The test for a dependent - annual income under ¥1.3 million - is the same at Kyokai Kenpo and at a society, because the 1977 notice it rests on draws no distinction between insurers[MHLW, Notice Hohatsu No. 9 of 1977]. Nor does the treatment of a spouse as a Category III insured person of the National Pension change.

What differs is practice. The notice does not say what counts towards "annual income", so each insurer decides how to check. One society tests a child supported by two working parents on the previous year's annual income, and provides that if the filing is more than a month late the date of certification becomes the day the papers arrive[Tokyo Stationery Industry HIS].

So "the paperwork that passed at my last employer is not enough" does happen. The conditions are set out in the conditions for a health insurance dependent.

What changes and what does not when you move jobs

Changing jobs changes your insurer. Separating what moves from what does not makes the checks before you join much shorter.

If your next job is not settled, voluntary continuation is an option. It lasts up to two years, and you pay the whole premium yourself[Health Insurance Act, Articles 38 and 161]. With a society, supplementary benefits may carry on, which is worth weighing against National Health Insurance.

There is one thing to do first. Check who issued your insurance card to see whether you are with Kyokai Kenpo or a society, and if it is a society, look up the employer's share and the supplementary benefit cap in its rules. The procedures are in tax and paperwork when you change or leave a job.

Summary

• The differences come down to two points: how the premium rate is set and the employer's share of the burden. The statutory benefits and the legal range for rates are the same.
• Kyokai Kenpo's Reiwa 8 (2026) rates range from 9.21% in Niigata to 10.55% in Saga, averaging 9.90%. The average for health insurance societies is 9.32%.
• Only health insurance societies can require the company to bear more than half the premium. With a monthly salary of ¥350,000, the rate difference comes to ¥18,360 a year, and the burden-share difference to ¥57,240 a year.
• The lower cost of health insurance societies is maintained through deficits. Of 1,364 societies, 1,010 are running a deficit.
• Only health insurance societies offer supplementary benefits. Check which type you have from the issuer of your insurance card, and if it's a society, review its bylaws.

References (sources)

• Kyokai Kenpo, FY2026 premium rates / announcement - rates by prefecture, long-term care 1.62%, average 9.90%
• Kenporen, state of society budgets (early tally) / financial outlook - average 9.32%, 1,364 societies, effective rate 9.90%, 1,010 in deficit
• Health Insurance Act - Articles 26, 38, 53 and 160 to 162
• Japan Pension Service, premium table - the grade for a standard monthly remuneration of ¥360,000
• MHLW, review of the high-cost medical expense benefit - the cap of ¥85,800 plus 1%
• MHLW, on the certification of dependents - the basis for the ¥1.3 million test
• Supplementary benefits in practice: Tokyo Information Service Industry HIS / Fujitsu HIS / Nippon Steel HIS

Note: the estimates apply published rates, grade tables and formulas ourselves. The employer's share and supplementary benefits are set in each society's own rules, so check the explanation your own society gives.