Kenmin Kyosai in Year-End Adjustment: Where to Write It

How to fill it in: copy the bold-framed amounts on the certificate into two boxes

Saitama Kenmin Kyosai's example fills in each field of the form like this[Saitama Kenmin Kyosai, "Filling in the insurance premium deduction form" (in Japanese)].

One plan's premium is split between General and Nursing/medical care because a single plan includes both death cover and hospital/surgery cover. The ratio is fixed for each plan, so you do not need to calculate it. Copy the amounts on the certificate as they are.

For general life and nursing/medical care premiums, the certificate must be attached whatever the amount. You can also submit an electronically issued certificate (data); Kanagawa Kenmin Kyosai and others let you download it from their member page[Kanagawa Kenmin Kyosai (in Japanese)].

How much comes back: ¥2,000 to ¥3,000 a year on a ¥2,000-a-month plan

Here is the calculation for a ¥2,000-a-month plan where the dividend refund is about 40% of premiums. Saitama Kenmin Kyosai's refund rate for fiscal 2025 was 44.84%[Saitama Kenmin Kyosai, business overview (PDF, in Japanese)].

Note: Income tax is calculated at the rate × 1.021 including the special reconstruction income tax, and resident tax at 10%. The General/Nursing-medical split is a hypothetical figure; the actual split follows your certificate. Income tax deduction calculation: National Tax Agency No. 1140[National Tax Agency No. 1140 (in Japanese)].

Under the new-system life insurance premium deduction, payments of up to ¥20,000 per category are deducted in full for income tax, and up to ¥12,000 for resident tax. Kenmin Kyosai premiums after the dividend refund often fall within this range, so the amount you write becomes the deduction as is. The full formula is explained in calculating the life insurance premium deduction.

Combined with private life insurance, some boxes do not increase

The life insurance premium deduction is capped per category. For income tax, General, Nursing/medical care and Individual annuity are each up to ¥40,000; for resident tax, each up to ¥28,000 with a combined cap of ¥70,000. If your private life insurance premiums exceed ¥80,000 a year, your "General" income tax deduction has already reached the ¥40,000 cap.

• If your General allowance is full: writing the co-op's General amount does not increase the deduction. But it is not wrong to write it, so you can write it anyway.
• If you have no medical insurance: the co-op's Nursing/medical care amount becomes your Nursing/medical care deduction as is. This is where writing the co-op premiums pays off.
• Resident tax combined cap of ¥70,000: the three categories together are capped at ¥70,000, so if your private insurance is near the cap in all three, adding the co-op does not change your resident tax.

From the 2026 tax year (令和8年分), people with dependents under 23 see the income tax "General" cap rise from ¥40,000 to ¥60,000 (the combined ¥120,000 cap is unchanged). In the year-end adjustment it applies to salary paid on or after 1 December, and a field for this special rule has been added to the form[National Tax Agency, changes to year-end adjustment forms (in Japanese)]. Parents whose General allowance was filled at ¥40,000 may find the co-op's General amount now counts.

What you cannot claim: injury and fire plans, and how the earthquake rider is treated

Note: Injury and fire plans follow Saitama Kenmin Kyosai's guidance; the earthquake rider follows Chiba Kenmin Kyosai's[Chiba Kenmin Kyosai, earthquake rider (in Japanese)]. For some plans, such as Kanagawa Kenmin Kyosai's Hospital Medical Cover II, the certificate comes directly from the underwriting life insurer.

If no certificate arrives for the earthquake rider, ask your Kenmin Kyosai whether it issues a certificate for the earthquake insurance premium deduction. Treatment can differ by prefecture. The earthquake insurance premium deduction calculation is covered in life insurance and earthquake insurance premium deductions.

If you miss the year-end adjustment, you can claim the same deduction by attaching the certificate to your tax return the following year. How to check in your December pay slip that the deduction was applied is explained in when and how much the year-end adjustment refund is.

Summary

• Kenmin Kyosai life and medical plans go in two places on the form's life insurance premium deduction section: "General" and "Nursing/medical care". The category is "New"
• Write "paid this year" after the dividend refund. The split is in the certificate's bold frame, so copy it as is
• On a ¥2,000-a-month plan with a 40% refund, the deduction is about ¥14,000 a year and the tax back is ¥2,000 to ¥3,000 a year
• If private insurance fills your General allowance (¥40,000 for income tax), the co-op's General amount adds nothing. The Nursing/medical care amount still counts
• Injury and fire plans are not eligible. The earthquake rider on a fire plan is eligible for the earthquake insurance premium deduction

References (sources)