[iDeCo] September 2026 Update: JPY 3,757,751 — My Hands-Off Japanese Pension Account Is Up +60.4% on Contributions

Hey there, it’s Hirokichi!

Here is my iDeCo update for the end of September 2026. iDeCo (Japan’s individual defined-contribution pension plan — contributions are fully tax-deductible, but funds are locked until age 60) closed the month at JPY 3,757,751, down JPY 65,020 from August. A jump in U.S. long-term yields weighed on stocks in September, but my gain on top of what I have contributed is still +JPY 1,415,101 (+60.4%).

September 2026 Result: JPY 3,757,751 Market Value (+60.4% Gain)

At the end of September, my iDeCo account was worth JPY 3,757,751, with an unrealized gain of +JPY 1,415,101. At the end of August it was JPY 3,822,771, so the account fell JPY 65,020 (-1.7%) in one month. That is a small step back from the recent high, but compared with a year ago (September 2025: JPY 2,902,772), it is up JPY 854,979 (+29.5%).

The chart shows that the account dipped to JPY 3,114,775 in March 2026, rebounded strongly in April and May, and reached JPY 3,822,771 in August. From the March low, that is a recovery of +JPY 642,976 (+20.6%), so September’s small decline looks like one step in a longer climb.

Contributions vs. Gains: About JPY 2.34M Became About JPY 3.76M

The real report card for iDeCo is the gap between the market value and the money I have put in. Calculated as market value minus unrealized gain (the cost basis), my cumulative contributions are JPY 2,342,650. Against a market value of JPY 3,757,751, the difference of JPY 1,415,101 is my investment gain.

The chart shows that contributions grow slowly while the market value pulls well above them. Over the past year, cumulative contributions rose by only JPY 162,948, but the market value rose by JPY 854,979. The remaining gap of about JPY 690,000 is what the market added while I kept investing.

Note that contributions have been growing more slowly since May 2026. My current contribution is JPY 5,000 per month. I am putting our children’s exam-related costs first for now, so I keep this at a comfortable level and keep going.

My Holding: One Fund, eMAXIS Slim U.S. Equity (S&P 500)

My iDeCo holds just one fund: eMAXIS Slim U.S. Equity (S&P 500), at 100% of the account. It spreads money across 500 large U.S. companies, and its expense ratio (the ongoing cost of holding a fund) is low, which suits an account I plan to leave alone for a long time.

Because there is only one fund, my balance moves mostly with U.S. stocks (the S&P 500) and the dollar-yen rate. It is simple, but it also means a weak month for U.S. stocks shows up directly in my balance. I have accepted that trade-off.

Since iDeCo money cannot be withdrawn until age 60, I do not have to think about when to buy or sell. Investing the same amount every month means buying fewer units when prices are high and more when prices are low, which smooths out the average purchase price. That “set it and forget it” quality is the main reason I chose this one fund.

September Market Recap and My Account

The S&P 500 fell about 0.4% in September and closed the month near 7,652. According to press reports, the Dow lost about 4.3% while the Nasdaq Composite gained about 1.9%. Only AI-related tech did well, while financials, materials and real estate were sold as long-term yields and oil prices rose (sources: Investrade, “Market Review: September 30, 2026” and Investing.com).

By month-end, the U.S. 10-year Treasury yield had climbed to nearly 5.3%, its highest level since 2002. August PCE inflation rose 3.4% from a year earlier, below the 3.7% that markets expected, yet long-term yields kept rising (source: Zaikei, in Japanese). The dollar-yen rate was around 157 at the end of September.

While the index fell about 0.4%, my account fell 1.7%. A fund’s net asset value is not always reflected on the same timing as the index, and the exchange rate also matters, so a fund’s monthly return rarely matches the index exactly. Rather than worrying about small differences, I read September simply as a month when stocks were heavy because of rising rates.

Higher interest rates raise borrowing costs for companies and make stocks look more expensive. Still, expectations for AI remain strong and U.S. economic data has been solid. Nobody knows which way the market will move next, so instead of trying to guess, I simply keep making my monthly contribution.

Checking the Tax Benefit: At Least JPY 9,000 a Year from JPY 60,000

The biggest perk of iDeCo is that every contribution is fully tax-deductible, meaning it can be subtracted from your income when your taxes are calculated. You can find the details on the official iDeCo website (National Pension Fund Association, in Japanese).

My current contribution is JPY 5,000 per month, or JPY 60,000 per year. At a combined rate of 15% (5% income tax plus 10% resident tax), that is JPY 60,000 x 15% = JPY 9,000 in tax saved per year. For someone in the 10% income-tax bracket, the combined rate is 20%, or JPY 12,000 per year. Tax rates differ from person to person, so please treat this as a conservative estimate. Even if my investments earned nothing, this saving would still be mine every year.

The chart shows that after 10 years, the tax savings alone add up to JPY 90,000. It looks small, but it is a benefit that stays in my pocket regardless of market gains. Gains earned inside iDeCo are also not taxed while they are in the account (taxes may apply when you receive the money, depending on how you take it).

The Road to Age 60: A 10-Year Rough Projection

iDeCo funds generally cannot be withdrawn until age 60, which is still a way off for me in my 40s. As a rough illustration only, I calculated what happens if today’s JPY 3,757,751 grows at 3% a year and I keep adding JPY 60,000 a year.

Under these assumptions, the account would be worth about JPY 5.74 million (JPY 5,737,936) in 10 years. Of course, markets will not move like this every year, and there will be down months like this one and sharp drops like March. This chart is not a forecast, just a rough image of what steady investing might look like.

Because the money is locked until 60, my approach is not to get swayed by daily price moves. I think that is the right way to live with iDeCo.

I am keeping my contribution low for now only to get through the peak of our education costs. Once our children’s exams are over, I plan to review my contribution and other monthly investments. Even a small amount, if you keep it going, matters most in the long run.

Summary

In September 2026, my iDeCo ended at JPY 3,757,751 (down JPY 65,020 from August) with a gain of +JPY 1,415,101 (+60.4%). Rising U.S. yields caused a small pullback, but the account is up 29.5% from a year ago and 20.6% from the March low, which is on track over the long run.

My contribution is small at JPY 5,000 a month, but I get the tax benefit while the account quietly grows on its own. Let’s keep going steadily, no rush. See you next time!

My total assets, all in one place: [Net Worth Update] August 2026
The full record of my net worth updates (since 2021)

日本語版はこちら → 【iDeCo】2026年9月の運用実績！評価額3,757,751円、拠出累計+141万円の運用益（+60.4%）に

* This article is for informational purposes only and is not investment or tax advice. Please make your own decisions at your own responsibility.