Your Japanese bonus (shoyo): why the take-home is smaller than the number — and the caps that quietly help

In some countries a bonus is taxed lightly, or treated as a separate windfall. In Japan it isn't. A Japanese bonus (賞与, shoyo — the summer and winter bonuses many companies pay) is run through the same social-insurance and withholding machinery as your monthly salary. That's why the amount that lands in your account can be noticeably less than the figure your manager quoted. Mio doesn't guess — here's exactly what comes off, read from the Japanese-language official sources, in plain English.

What comes off a bonus — the four deductions

These are the same categories as your monthly payslip, applied to the bonus. All rates below are qualitative and vary by prefecture, insurer, age, and year — verify the exact figures on your own bonus slip.

• Health insurance — 健康保険 (kenko hoken)
  Charged on your "standard bonus amount" (標準賞与額, the gross bonus rounded down to the nearest ¥1,000). Shared roughly 50/50 with your employer, so your share is about 5% (the rate varies by prefecture and insurer). If you're 40 or older, an extra long-term-care line (介護保険, kaigo hoken) is added.
• Pension — 厚生年金 (kosei nenkin)
  Also charged on the standard bonus amount at the 18.3% total rate, split equally, so your share is roughly 9.15%. Usually the single biggest deduction from a bonus.
• Employment insurance — 雇用保険 (koyo hoken)
  Charged on the gross bonus. For a general-industry employee the worker's share is 0.55% for FY2025 (1 Apr 2025–31 Mar 2026); higher for construction/agriculture-forestry. The rate is set nationally and changes periodically.
• Income tax — 所得税 (shotokuzei), withheld
  Withheld at source using the NTA's bonus withholding-rate table. The rate is chosen from your previous month's salary (after social insurance) and your number of dependents — then applied to the bonus after its social insurance. See the trap below.

The non-obvious part #1: the tax rate comes from last month's salary

Most people assume a bigger bonus is taxed at a higher rate because it's big. That's not how the withholding works. The NTA uses a table (賞与に対する源泉徴収税額の算出率の表) where the withholding percentage is looked up from your prior month's ordinary salary (after social-insurance deductions) and how many dependents you've declared. That percentage is then applied to your bonus.

Two consequences foreigners miss:

• If last month's salary was unusually high (or you had a pay bump), your bonus can be withheld at a higher rate than you'd expect — and vice-versa.
• This withholding is only a provisional estimate. Your true annual income tax is calculated at the year-end adjustment (年末調整, nenmatsu chosei) in Nov–Dec. If too much was withheld across your salary and bonuses, the difference comes back as a refund — often visible in your December or January pay. So a scary-looking bonus tax line is not necessarily your final tax.

The non-obvious part #2: social-insurance caps that help big bonuses

Social insurance on a bonus is not unlimited. Each part has its own ceiling, and above it that premium simply stops:

• Health insurance — annual cumulative cap of ¥5,730,000 across the fiscal year (1 Apr–31 Mar). Once your total standard bonus amount for the year passes ¥5.73M, no further health-insurance premium is charged on bonuses beyond it.
• Pension — per-payment cap of ¥1,500,000. For any single bonus, only the first ¥1.5M is subject to pension premium; the portion above ¥1.5M is not.

For most employees these caps never bite. But if you receive a very large bonus, part of it is effectively exempt from those premiums — one of the few places in the Japanese system where hitting a ceiling works in your favour. (Employment insurance and income tax have no such bonus cap.)

Illustrative bonus — line by line

Figures below are illustrative only (not a real bonus and not fixed rates). Use them to recognize the shape of a bonus slip, then read your own.

Note: unlike your monthly salary, resident tax (住民税) is not deducted from a bonus — it's billed separately on your monthly pay from year 2. So the bonus deductions are the four above, not five.

Mio's read

A Japanese bonus is real money, but it's gross money. Full pension and health insurance apply, employment insurance takes a small slice, and income tax is withheld at a rate borrowed from last month's salary — then all of it is trued up at year-end. Plan around ~70–80% landing in your account, remember that a big single bonus is partly capped for social insurance, and treat the withheld tax as provisional, not final. When a number looks off, don't guess — check your bonus slip and ask HR.

Next: want the whole deduction picture? Read your monthly payslip, line by line → · The income "walls" for dependents →