This is a YMYL topic — one where a wrong assumption can cost you real money or a penalty. Mio doesn't guess and doesn't invent numbers. Below is the framework straight from Japan's National Tax Agency (NTA), in plain English, so you know what questions to bring to a professional. It is not personal tax advice.
Japan first asks whether you're a resident or a non-resident, and then splits residents into two. Your category depends on where you're domiciled and how long you've lived in Japan — not on your visa type or passport.
| Category | Roughly who | Generally taxed on… |
|---|---|---|
| Non-resident | No domicile in Japan and hasn't lived here continuously for 1 year | Japan-source income only |
| Non-permanent resident | Resident, non-Japanese, lived in Japan ≤ 5 of the last 10 years, no permanent intent | Japan-source income + foreign-source income paid in or remitted to Japan |
| Permanent resident (for tax) | Resident who has lived in Japan > 5 of the last 10 years (or is domiciled/Japanese) | Worldwide income |
Illustrative summary of the NTA framework — thresholds and definitions have technical detail (e.g. how "domicile," "residence," and the 5-of-10-years count are measured). "Permanent resident for tax" is a tax status and is different from the immigration "Permanent Resident" visa. Confirm your own category with the NTA or a professional.
The practical takeaway: the longer you stay, the wider Japan's tax net gets.
If you're a non-permanent resident, foreign-source income becomes taxable in Japan to the extent it is remitted to Japan — and "remittance" is broader than most people think. Money you move from an overseas account into Japan in the same year can be deemed to include your foreign income, following the NTA's ordering rules, and taxed here.
Why it's a trap: people assume "I already paid tax abroad, so Japan won't touch it." But if you bring that money into Japan, some of it may become taxable here too. The mechanics (how much is deemed remitted, how it's ordered) are technical — this is exactly the kind of thing to verify with the NTA or a tax professional before moving large sums.
This is the one people get wrong most often. If you are physically in Japan doing the work, the salary is generally treated as Japan-source income — because the source rule looks at where the work is performed, not where the employer sits or where you're paid.
So "I work remotely from Tokyo for a US company, they pay my US bank account, so it's US income" is usually not how Japan sees it. Because a foreign employer typically doesn't withhold Japanese tax, the NTA notes such workers often need to file a return in Japan themselves. Whether a tax treaty changes the outcome depends on your specific facts — do not assume. See year-end adjustment vs. filing a return →
Being taxed by two countries on the same income is the fear — and there are two main mechanisms designed to prevent it:
Together these are meant to ensure you're not fully taxed twice — but they don't apply automatically. You usually have to claim them correctly, with documentation, in the right country. That's professional territory.
Mio's honest verdict: the framework above tells you which questions matter, not what to do. Get a qualified tax professional (or ask the NTA directly) if any of these apply:
Bottom line: your category decides how wide Japan's tax net is; remittances and remote work are the two things people underestimate; treaties and the foreign tax credit exist to stop double tax but must be claimed. This is complex — verify with the NTA or a tax professional before acting.