How are social insurance premiums on a bonus determined — the cap on the standard bonus amount and the bonus payment report / non-payment report

In short: Social insurance premiums on a bonus are calculated by multiplying the "standard bonus amount" — the pre-tax bonus with amounts under 1,000 yen dropped — by the premium rate, split equally between the company and the employee. The cap is a cumulative 5.73 million yen per fiscal year (April 1 to March 31) for health insurance and 1.5 million yen per month for employees' pension, so the way the period is taken differs. The bonus payment report is filed with the Japan Pension Service within 5 days of payment. This article is general guidance.

For owners and HR staff at small and medium-sized companies that pay a bonus, this article organizes how the health-insurance and employees'-pension premiums on a bonus are determined, the cap on the standard bonus amount, and the bonus payment report and bonus non-payment report. How the monthly standard remuneration is decided (the base-amount report and occasional revision) is organized separately in what is the difference between the base-amount report and occasional revision — how the standard monthly remuneration is decided. This article only introduces the system; individual amounts and eligibility depend on the circumstances.

On what basis are social insurance premiums on a bonus calculated?

Premiums on a bonus are calculated per bonus, separately from the monthly salary (the standard monthly remuneration). The basis is the "standard bonus amount," which is the bonus actually paid (the pre-tax gross) with amounts under 1,000 yen dropped. This is multiplied by the premium rates for health insurance, employees' pension, and so on, and borne half each by the company and the employee (an equal split).

Item	Content
Basis	Standard bonus amount = the pre-tax bonus with amounts under 1,000 yen dropped
Formula	Standard bonus amount × premium rate (health insurance, employees' pension, etc.) = premium
Burden	Split equally between company and employee
Covered bonus	A payment made 3 or fewer times a year (whatever its name; 4 or more times is treated as standard monthly remuneration)
Employees' pension rate	18.3% (split equally; fixed since September 2017)
Health insurance rate	Differs by the insurer (the prefecture-by-prefecture rate of Kyokai Kenpo, or the health insurance society)

The point is that only payments made "3 or fewer times a year" count as a bonus. A payment made 4 or more times a year is taken into the standard monthly remuneration (monthly salary) rather than treated as a bonus. Payments not regarded as consideration for work, such as a wedding gift, are outside social insurance altogether. For those aged 40 to under 65, nursing-care insurance is added, and from the bonus for April 2026 (Reiwa 8) the child-and-childcare support contribution is added, so confirm the rates with the latest information from the insurer and for the fiscal year (Ministry of Health, Labour and Welfare / Japan Pension Service guidance, referenced October 2026).

Is there a cap on the standard bonus amount (it differs for health insurance and pension)?

There is a cap, but health insurance and employees' pension differ in how the period is taken. Mix these up and the premium comes out wrong.

Category	Cap	How the period is taken
Health insurance (nursing-care insurance and the childcare support contribution follow the same idea)	5.73 million yen	Cumulative over the fiscal year (April 1 to March 31)
Employees' pension	1.5 million yen	Per month (per payment month)

Health insurance caps the "fiscal-year cumulative" at 5.73 million yen. For example, if someone who has already received 5 million yen in bonuses in the same fiscal year is paid a further 3 million yen, only the 730,000 yen up to the cap, out of the 8 million yen total, is subject to health-insurance premiums. Employees' pension caps "per month" at 1.5 million yen, and where two or more bonuses are paid in the same month, the cap applies to the combined amount.

Where the person remains insured continuously at the same establishment, no special report is needed from the employer even if the fiscal-year cumulative exceeds 5.73 million yen (it is adjusted in the system). However, where the cumulative exceeds 5.73 million yen for someone who was insured at multiple establishments in the same fiscal year, the employer files the "health insurance standard bonus amount cumulative report" based on the person's declaration (Japan Pension Service guidance, referenced October 2026).

By when must the bonus payment report be filed?

When a bonus is paid, file the "insured person bonus payment report" with the Japan Pension Service (the administrative center or the pension office) within 5 days of payment. The same report is used when a bonus is paid to an employed person aged 70 or over.

Report	Deadline / content
Insured person bonus payment report	Within 5 days of the bonus payment date; reports the amount paid, etc.
Where to file	Japan Pension Service (administrative center / pension office); also the society if in a health insurance society
Summary sheet	Since April 1, 2021 (Reiwa 3), the summary sheet for the insured person bonus payment report is no longer required

The standard bonus amount is decided on the basis of this report, and the premium is fixed. What is withheld from the employee is withheld at the time of the bonus payment; what the company pays is, in principle, due by the end of the following month. If the report is late, the fixing and payment of the premium slip back, so the practical basis is to file within the deadline each time a bonus is paid. A company in a health insurance society needs to report to both the Pension Service and the society.

If no bonus was paid in a month, is any report needed?

At an establishment that has registered a scheduled bonus-payment month in advance, if no bonus was paid in that month, file a "bonus non-payment report" instead of the "bonus payment report." Since April 1, 2021 (Reiwa 3), the treatment changed to asking for this report in place of the former summary sheet.

• What to file: when no bonus was paid in the registered scheduled bonus-payment month = the bonus non-payment report
• What happens if you do not: an employer that has not filed by the month after the registered scheduled bonus-payment month is sent a demand letter in the month after that
• Changing the scheduled month: to change the scheduled bonus-payment month itself, change it separately via the "health insurance / employees' pension insurance bonus scheduled-payment-month change report"

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It is easy to think "since no bonus was paid, nothing needs to be done," but as long as a scheduled payment month is registered, a non-payment report is required. To avoid receiving a demand letter, it is safe to file the bonus non-payment report for a month in which no bonus was paid (Japan Pension Service guidance, referenced October 2026).

Who do you consult about the income tax (withholding) on a bonus?

The work around a bonus is handled by different parties. The calculation of social-insurance (health insurance and employees' pension) premiums and the filing of the bonus payment report and bonus non-payment report is an area a Shakai Hoken Roumushi can support, but the income tax (withholding) on a bonus and the year-end adjustment are the tax accountant's area.

Point	Who handles it
Calculating the social-insurance premiums on a bonus, and preparing and filing the bonus payment report / bonus non-payment report	Shakai Hoken Roumushi (our office)
The income tax (calculating the withholding tax) on a bonus, the year-end adjustment, and tax filing	Tax accountant (a separate business entity, contracted separately)
Finally fixing the standard bonus amount and the premium	Japan Pension Service / health insurance society (the company confirms)

The withholding income tax on a bonus is calculated with a rate based on the previous month's salary and the number of dependents — a calculation separate from social insurance. 四葉社会保険労務士事務所 supports the calculation of social-insurance premiums and the filing, but for income tax and the year-end adjustment we connect you to a tax accountant as a separate business entity, contracted separately (we take no referral fee). On the company's side, please confirm whether there is any change in the premium rate or the dependent situation and whether the amount paid is correctly reflected. This article only introduces the framework and does not decide individual amounts or whether a given treatment is permissible.

Frequently asked questions

Q. How do you calculate social insurance premiums on a bonus?
A. Multiply the "standard bonus amount" — the pre-tax bonus with amounts under 1,000 yen dropped — by the premium rates for health insurance, employees' pension, and so on, split equally between the company and the employee. The employees' pension rate is 18.3% (split equally); the health insurance rate differs by insurer. What counts is a bonus paid 3 or fewer times a year; a payment made 4 or more times a year is included in the standard monthly remuneration (monthly salary).

Q. Is there a cap on the standard bonus amount?
A. Yes. Health insurance caps the fiscal-year cumulative (April 1 to March 31) at 5.73 million yen, and employees' pension caps it per month (per payment month) at 1.5 million yen. Note that the health-insurance cap is on the fiscal-year cumulative while the pension cap is per month. Where two or more are paid in the same month, the cap applies to the combined amount.

Q. By when must I file the bonus payment report?
A. File the insured person bonus payment report with the Japan Pension Service within 5 days of the bonus payment date. The same report applies when a bonus is paid to an employed person aged 70 or over. Since April 1, 2021, the summary sheet for the insured person bonus payment report is no longer required. A company in a health insurance society must also report to the society.

Q. If no bonus was paid in a month, is any report required?
A. At an establishment that has registered a scheduled bonus-payment month, if no bonus was paid in that month, file a "bonus non-payment report." If nothing is filed by the month after the registered scheduled month, a demand letter is sent the month after that. To change the scheduled payment month itself, change it via the scheduled-payment-month change report.

Sources

• Definition of the standard bonus amount: the bonus actually paid (the pre-tax gross) with amounts under 1,000 yen dropped (Japan Pension Service, "procedures when an employee is paid a bonus," referenced October 2026).
• Cap: health insurance caps the fiscal-year (April 1 to March 31) cumulative at 5.73 million yen; employees' pension caps it per month at 1.5 million yen; where two or more are paid in the same month, the cap applies to the combined amount (the standard-bonus-amount provisions of the Health Insurance Act and the Employees' Pension Insurance Act; Japan Pension Service guidance, referenced October 2026; confirm amounts and treatment with the latest information).
• Covered bonus: a payment made 3 or fewer times a year (4 or more times is treated as standard monthly remuneration; payments not regarded as consideration for work are excluded) (Japan Pension Service guidance, referenced October 2026).
• Deadline for the bonus payment report: within 5 days of the bonus payment date; the summary sheet for the insured person bonus payment report has not been required since April 1, 2021 (Reiwa 3) (Japan Pension Service guidance, referenced October 2026).
• Bonus non-payment report: filed where no bonus was paid in the registered scheduled bonus-payment month; an employer that does not file by the following month is sent a demand letter the month after that (Japan Pension Service guidance, referenced October 2026).
• Employees' pension rate: 18.3% (split equally; fixed since September 2017). The health insurance rate differs by insurer. For those aged 40 to under 65 nursing-care insurance is added, and from the bonus for April 2026 the child-and-childcare support contribution is added (Ministry of Health, Labour and Welfare / Japan Pension Service guidance, referenced October 2026).
• Business of a Shakai Hoken Roumushi: Article 2 of the Certified Social Insurance and Labor Consultant Act.

This article does not decide whom to consult. 四葉社会保険労務士事務所 can advise on calculating the social-insurance premiums on a bonus and preparing and filing the bonus payment report and bonus non-payment report. For the income tax (withholding) and the year-end adjustment on a bonus, we connect you to a tax accountant as a separate business entity, contracted separately (we take no referral fee). For fees, see the fee schedule; for frequently asked questions, see the FAQ.

This article is general information. Individual judgments — the premium amount on a bonus, how the cap applies, whether a report is required — depend on the amount paid, the insurer, and the fiscal year. Application of the system and individual judgments are made by a qualified professional after a consultation, in light of the latest primary sources (the Ministry of Health, Labour and Welfare, the Japan Pension Service, e-Gov, etc.) and individual circumstances. Written by Joji Uramatsu (Shakai Hoken Roumushi, Gyoseishoshi, Registered Real Estate Transaction Specialist).