Once a year, every employer enrolled in health and pension insurance submits a santei kiso report, formally the notification of the basis for calculating remuneration. It lists what each insured employee was paid in April, May and June. The Japan Pension Service averages the three months, assigns a grade of standard monthly remuneration, and that grade applies from September to the following August. The process is called the regular determination.
For 2026 the filing window was 1 to 10 July. Employees who joined on or after 1 June are excluded, since their grade was set on hiring, as are those whose grade is already being revised for a change in fixed pay from July to September. Months with fewer than 17 paid days are generally left out of the average. Where pay in those three months is unusual for seasonal reasons, the employer can ask for the average of the full year to be used instead.
Because everything paid in the three months counts, including overtime and allowances, a busy spring can lock in a higher grade for a year. The reverse also holds: a quiet April to June means lower contributions until the next September.
What it means for a foreign employer
- Spring overtime costs twice. Heavy overtime in April to June raises both the employer's and the employee's contributions for the following twelve months. Some teams with a March year-end close feel this every year.
- Time pay changes with the cycle in mind. A large pay rise effective in April feeds the reset directly; one effective later is picked up by the occasional revision only if it moves the employee by two grades.
- The deadline is short and fixed. A subsidiary using an overseas payroll provider needs April to June data in Japanese format by early July.
- Expect net pay to change in October. The new grade applies from September contributions, usually deducted from October pay, which employees notice.
Sources
- Health Insurance Act, Article 41; Employees' Pension Insurance Act, Article 21.
- Japan Pension Service, notice on submission of the fiscal 2026 santei kiso report (May 2026).