Treating NISA as risk-free, misunderstanding limits, using the wrong dividend method, chasing performance, and ignoring departure and foreign-tax rules.
The frequent mistakes are treating tax-free as risk-free, confusing market value with allowance usage, receiving dividends the wrong way, picking funds by last year’s return, opening with the wrong broker, and ignoring departure or foreign-tax rules.
The first mistake is emotional: treating NISA as safe because it is tax-advantaged. NISA is only a wrapper; the investments inside can fall like any others, and a tax-free 30% loss is still a 30% loss. Size your equity exposure to what you can hold through a downturn, not to the size of the allowance.
The second is mechanical: confusing market value with allowance usage. Capacity is measured at acquisition cost, so a holding that doubles has not used any extra room, and you cannot "top up" to a market value of ¥18m. Related errors include expecting unused annual allowance to carry forward (it does not) and expecting immediate allowance restoration after selling (it returns next year, at cost).
A common income mistake is receiving share, ETF, or REIT dividends through a bank account or warrant instead of the proportional allocation method, which triggers 20.315% withholding despite NISA — and a later return cannot fix it. Set the receipt method before the dividend is paid.
On product selection, avoid choosing funds by last year’s return: recent performance is an unreliable basis for future relative results, and a top-ranked fund can lag the next year. Equally, resist overcomplicating the portfolio with many overlapping thematic funds; a single broad low-cost index fund often does the core job with less duplication and lower cost.
Two structural mistakes cause outsized problems. The first is ignoring departure rules: NISA generally cannot continue after you leave Japan except in specific qualifying temporary cases filed in advance, so building a large NISA balance without a plan for leaving can force an awkward unwind. Get your broker’s written departure procedure early.
The second is a US-taxpayer trap: buying a Japanese mutual fund in NISA without checking PFIC treatment and US reporting. NISA’s Japanese exemption gives no US exemption, and a "simple" index fund can create Form 8621 obligations. If you are a US person, complete cross-border analysis before your first Japanese-fund purchase.
Brokerage (NISA/iDeCo) · Rakuten Securities
A leading low-cost brokerage for NISA and index-fund investing, integrated with Rakuten points and Rakuten Bank.
Fees: Many domestic funds and trades are low- or no-commission — verify current fee schedule.
Brokerage (NISA/iDeCo) · SBI Securities
Japan’s largest online brokerage by accounts, with a very broad low-cost fund lineup and full NISA/iDeCo support.
Fees: Many trades and funds are low- or no-commission — verify current fee schedule.
Brokerage (NISA/iDeCo) · Monex
An established online brokerage often chosen for US-stock access and research tools, with NISA and iDeCo support.
Fees: Commissions vary by product; some funds/trades are low-cost — verify current schedule.
Generally yes, if you are a tax resident of Japan (with a My Number) and at least 18. NISA is tied to residency, not citizenship, so most foreign residents qualify — with two big cautions: US citizens and green-card holders face US tax complications with Japanese funds, and NISA generally cannot continue after you leave Japan. Confirm eligibility and the current rules on the FSA site and with your chosen brokerage.
NISA is a benefit for residents. When you lose Japanese tax residency you generally cannot keep contributing, and brokerages differ on whether the account is closed, frozen, or must be sold — some allow a temporary overseas-resident continuation for limited periods. Because the tax treatment of unwinding matters, plan your exit before building a large balance and ask your brokerage about their specific offshore policy.
Be very careful. Japanese mutual funds and ETFs are usually PFICs (Passive Foreign Investment Companies) for US tax, which triggers punitive US taxation and heavy Form 8621 reporting — and the NISA tax exemption does not apply to the US. Many US persons in Japan avoid Japanese pooled funds and instead hold US-domiciled assets, but rules are complex. Get advice from a cross-border US/Japan tax professional before investing.