Tax Residency Between Korea and the US

Residency is the question that decides everything else — which country taxes your worldwide income, which taxes only local income, and which forms you owe. Korea and the US use different tests, applied independently, so it is entirely possible to be treated as a resident of both in the same year. That is not a paradox to ignore; it is a specific situation the tax treaty exists to resolve.

Who this affects

Anyone who moved between Korea and the US partway through a year
Korean employees on assignment in the US, and US employees posted to Korea
Students and researchers whose visa status changed mid-year
People who keep a home, family, or business in one country while working in the other

(001)

Korea looks at domicile and days

Korea treats you as a resident if you have a domicile in Korea, or a place of residence there for 183 days or more. Domicile is judged on objective facts about your life — family, assets, occupation — not merely on where you are registered.

(002)

The US test counts across three years

The substantial presence test does not look only at the current year. It weights days from the two preceding years as well, which is why people who split time evenly are often surprised to find themselves US residents. Citizens and green card holders are residents regardless of days.

(003)

Both tests can be satisfied at once

The two systems do not consult each other. When both call you a resident, the US–Korea income tax treaty supplies tie-breaker rules — looking at permanent home, then centre of vital interests, then habitual abode, then nationality — to assign a single treaty residence.

(004)

Residency can change mid-year

Arriving or leaving partway through a year can split it into resident and non-resident periods, each taxed on a different basis. Getting the split date right materially changes the outcome and is a common source of amended returns.

Common questions

Can I be a tax resident of both countries at the same time?

Yes, and it is common in the year of a move. Each country applies its own test independently. The treaty's tie-breaker rules then determine a single residence for treaty purposes.

I am a green card holder living in Korea. Am I a US resident?

Generally yes. Green card holders remain US tax residents on worldwide income regardless of where they live, until the status is formally abandoned or terminated.

Does the treaty mean I only pay tax in one country?

Not exactly. It assigns taxing rights and provides relief from double taxation, usually through credits or exemptions, but you may still have filing obligations in both countries even when tax is only ultimately paid in one.

Official sources

General information, not tax advice. Rules and thresholds change, and how they apply depends on your circumstances — confirm with a licensed professional before acting.