What is Nenkin? Japan's Pension System Explained for Expats

If you work and live in Japan, you have likely seen 'Nenkin' (年金) deductions on your monthly payslip. Understanding Japan's national pension system is essential for every expat, whether you plan to stay long-term or return home in a few years. This guide walks through the two tiers of Nenkin, how much you actually pay, what happens to your contributions when you leave Japan, and how to claim a refund.

The Two Categories of Japanese Pension

Japan operates a two-tiered pension system. Under national law, all residents aged 20 to 59 must participate in one of the following branches:

• National Pension (Kokumin Nenkin - 国民年金): The flat-rate base tier. It covers self-employed individuals, students, unemployed residents, and spouses of corporate employees. Contributions are a flat monthly fee (¥16,980 for the 2024–2026 fiscal years).
• Employees' Pension Insurance (Kosei Nenkin - 厚生年金): The salary-linked tier. It covers corporate employees and public servants. Contributions are 18.3% of your standard monthly remuneration (standard remuneration + bonuses), split 50/50 between you and your employer — so 9.15% each.

Types of Pension Coverage: Who Is Enrolled in Which?

Which tier you fall into is determined by your employment status, not by your visa or nationality:

• Category 1 insured (第1号被保険者): Self-employed, freelancers, students, and unemployed residents aged 20–59. You pay the flat Kokumin Nenkin fee yourself, usually by monthly bank transfer or a payment slip sent by the Japan Pension Service.
• Category 2 insured (第2号被保険者): Company employees and public servants aged 20–59. Your enrollment in Kosei Nenkin is automatic and handled by your employer; you are simultaneously enrolled in Kokumin Nenkin through Kosei Nenkin.
• Category 3 insured (第3号被保険者): Spouses of Category 2 insured whose own income is below the dependency threshold. They are covered by Kokumin Nenkin without paying the flat fee directly — the coverage is funded through their working spouse's Kosei Nenkin contribution.

The distinction matters because it determines not only how much you pay but also what you can claim back. Category 2 employees who leave Japan can reclaim the Kosei Nenkin portion via the Lump-Sum Withdrawal Refund, whereas Category 1 contributors who paid the flat Kokumin Nenkin fee out of pocket are subject to different rules. Category 3 spouses, by contrast, have no direct contribution to reclaim — but their coverage still counts toward the 10-year (120-month) minimum needed for a future old-age pension under the totalization rules.

How Much Do You Actually Pay?

For Category 1 (self-employed, students, etc.), the monthly premium is a fixed ¥16,980 (fiscal 2024–2026). Students can apply for the Special Payment for Students system to defer payments, and low-income residents can apply for full or partial exemptions.

For Category 2 (employees), the math is percentage-based. Kosei Nenkin takes 18.3% of your Standard Remuneration Monthly Amount (標準報酬月額) — a graded figure that buckets your salary into bands — plus 18.3% of standard bonuses. Your employer pays half (9.15%) and the other half is withheld from your pay. On top of this, you are automatically contributing to Kokumin Nenkin at a flat rate embedded inside the Kosei Nenkin calculation.

Example: An employee with a standard monthly remuneration of ¥320,000 will see roughly ¥29,300 withheld for Kosei Nenkin (9.15% of ¥320,000), with the employer matching it. Bonus months trigger an additional Kosei Nenkin deduction at the same rate.

What Happens to My Contributions if I Leave Japan?

Expats who pay pension premiums for at least 6 months and leave Japan permanently can claim a Lump-Sum Withdrawal Refund (Dattai Ichijikin - 脱退一時金). This refund allows you to reclaim up to 60 months (5 years) of your contributions, minus a 20.42% income tax withholding on the Kosei Nenkin portion.

The refund is calculated based on your average standard remuneration over the contribution period, not on the literal yen amount you paid. The schedule is published by the Japan Pension Service and tiers range from roughly ¥120,000 to ¥680,000 per month of refundable contribution for Kosei Nenkin participants. Importantly, you can only claim within 2 years of leaving Japan, and you must have lost your Japan residence status.

How the Lump-Sum Refund Is Calculated

The Dattai Ichijikin is not a straight refund of what you paid. Instead, the Japan Pension Service multiplies your average Standard Remuneration Monthly Amount over the contribution period by a tier-based coefficient, then caps the result at 36 or 60 months depending on your circumstances. The key formula components are:

• Average Standard Remuneration (平均標準報酬額): The mean of your monthly Standard Remuneration values across all months you contributed to Kosei Nenkin.
• Refund coefficient (支給率): A percentage that decreases as your average remuneration increases. Higher earners get a lower percentage back per month.
• Contribution period cap: A maximum of 36 months for Kokumin Nenkin-only periods, and up to 60 months when Kosei Nenkin contributions are included. Any months beyond the cap are not refunded.

As an illustrative example, suppose you contributed to Kosei Nenkin for 24 months with an average Standard Remuneration of ¥300,000. The refundable amount before tax might land in the ¥300,000–¥500,000 per contributed-month tier depending on the exact coefficient published in the year you apply. After applying the 20.42% income tax withholding, the net deposit to your overseas bank account is roughly 80% of the gross figure. The exact coefficient tables are updated periodically and published on the Japan Pension Service website.

Can You Get a Refund? Eligibility at a Glance

• You have paid Nenkin contributions for at least 6 months in the last 5 years (does not need to be consecutive).
• You do not have a registered address in Japan (you have departed).
• You have never been eligible for a Nenkin pension (kosei/kokumen nenkin old-age pension).
• You apply within 2 years of leaving Japan.

Social Security Agreements

Japan has bilateral social security agreements with more than 20 countries, including the US, UK, Germany, France, Australia, the Netherlands, and South Korea. These agreements serve two purposes: (1) they prevent double coverage so that an expat on a short assignment can stay covered by their home country's system, and (2) they allow merging contribution periods between Japan and the partner country to qualify for old-age benefits.

If your home country has an agreement with Japan, you may be exempt from Japanese Nenkin entirely during a temporary assignment (typically up to 5 years) by obtaining a Certificate of Coverage from your home country's pension authority before arriving in Japan. Check with your embassy or the Japan Pension Service website for your country's specifics.

The totalization benefit is particularly relevant for expats who split careers between Japan and a treaty country. For example, an American who works in Japan for 7 years (84 months) but then returns to the US would normally fall short of Japan's 120-month minimum for an old-age pension. Under the US-Japan agreement, those 84 months can be combined with US Social Security credits to help meet the minimum qualifying period in one or both systems. Without totalization, short-stay expats who never reach the 10-year threshold in Japan would see those contributions effectively lost — which is exactly why the Lump-Sum Withdrawal Refund exists as an alternative path.

Common Mistakes Expats Make With Nenkin

• Ignoring the 2-year claim window: The Dattai Ichijikin application must reach the Japan Pension Service within 2 years of your departure. After that, the right to claim expires permanently — even if you contributed for years.
• Forgetting to appoint a Tax Representative: The 20.42% withheld on the Kosei Nenkin portion is recoverable, but only if you designate a 納税管理人 (Nouzei Kanrinin) who can file a final tax return on your behalf after you leave.
• Assuming social security agreements apply automatically: The exemption from Japanese Nenkin during a temporary assignment requires a Certificate of Coverage issued before you arrive. Applying retroactively is often rejected.
• Stopping Category 1 payments mid-way: If you switch from employment to freelancing and stop paying Kokumin Nenkin, the gap counts as unpaid months. Short gaps can be back-paid (追納) within 10 years, but at higher rates.
• Not keeping pension records: Request your Nenkin Tsukiuchi (年金定期便) every year on your birthday month from the Japan Pension Service. It shows your total contribution months — essential for both refund claims and old-age pension eligibility checks.

Supplementary Pension Options: iDeCo and Kokumin Nenkin Fund

Beyond the mandatory tiers, Japan offers voluntary supplementary pension plans that provide significant tax advantages. The most popular is iDeCo (個人型確定拠出年金 - 個人型確定拠出年金), a defined-contribution plan that lets you invest a monthly amount (¥12,000–¥68,000 depending on your employment status) in a self-selected portfolio of mutual funds. Contributions are fully deductible from taxable income, investment growth is tax-free, and withdrawals are taxed at a favorable rate. For employees, the annual contribution cap is ¥276,000.

For Category 1 insured (self-employed), the National Pension Fund (国民年金基金) is another option offering additional annuity income in retirement. Contributions are also deductible, and the fund pays a lifelong annuity on top of the basic Kokumin Nenkin pension. The choice between iDeCo and the National Pension Fund — or both — depends on whether you prefer a lump-sum-style withdrawal (iDeCo) or a guaranteed annuity (Fund). You can explore contribution scenarios using our iDeCo Calculator.

How to Check Your Nenkin Record

The Japan Pension Service mails a Nenkin Teikibin (年金定期便 - Pension Regular Notice) to every insured person around their birthday month from age 45 onward, and annually to all insured persons via digital notice (if you have a Basic Pension Number registered with the Mynaportal). This document is your pension statement and shows:

• Total months of Kokumin Nenkin and Kosei Nenkin contributions.
• Any months with exemptions or grace periods applied.
• Estimated old-age pension amounts at age 60 and 65.
• Your pension number (年金番号), needed for all pension-related procedures.

If you have never received one, you can request a copy at any pension office (年金事務所) or via the Mynaportal. Review it annually to catch any employer reporting gaps — a common issue when switching jobs or during periods of unemployment between contracts.

Why This Matters for Expats

Nenkin deductions can take 13–15% of an employee's gross pay — a meaningful chunk of your monthly income. Knowing whether you can recover that money before leaving Japan, and understanding the timing rules for the Lump-Sum Withdrawal Refund, is the difference between walking away with hundreds of thousands of yen or nothing. If you are more than a year into your Japan stay, run the numbers on our Pension Lump-Sum Withdrawal Calculator now so you can plan your exit timing around the 60-month cap.