Keep a travel calendar and list accounts and income in both countries. Check payroll taxes now and ask how U.S. retirement accounts would work if you later return to Taiwan.
TSMC-specific foundation
Start U.S.–Taiwan planning with residency and source-of-income facts
A TSMC transfer does not by itself determine U.S. tax residency. Immigration status, the substantial-presence test, possible exceptions and Arizona's residency facts all matter. Once U.S. person status applies, worldwide income and foreign financial accounts can create reporting even when money never enters the United States. Payroll coding and a mailing address are evidence, not the complete legal conclusion.
U.S. tax residency can arise under the green-card or substantial-presence tests, with exceptions and elections that require individual analysis. Arizona residency has its own factual standards.
Keep a travel calendar and immigration records. Do not use payroll withholding or a mailing address as the only evidence of residency.
U.S. persons may have reporting obligations for foreign financial accounts and specified foreign assets. Foreign mutual funds, pensions, insurance and companies can have specialized U.S. tax treatment.
Inventory legal owner, institution, account type, maximum value, income and underlying holdings. A cross-border tax professional should determine the required forms.
How the pieces interact
Treat reporting, tax and account access as separate questions
Compensation can relate to work performed in more than one country or vest over a period that crosses the move date. Taiwan funds, pensions, insurance or business interests can also receive specialized U.S. treatment. The United States does not list Taiwan among its income-tax treaties in force, so employees should not assume treaty relief that might exist for another country. Foreign tax credits or domestic rules may still reduce double taxation, but qualified professionals must apply them to the facts.
Salary, bonuses, equity and relocation payments may relate to services performed across more than one location or period. Payroll reporting is a starting record, not a complete cross-border conclusion.
Retain assignment letters, pay statements, award agreements and travel records. Coordinate federal and Arizona withholding with projected tax.
A 401(k) or IRA may remain useful after a move, but provider access, address policy, investment availability and distribution withholding should be checked before leaving the United States.
IRS guidance states that plan distributions to foreign payees generally face 30% withholding unless documentation establishes U.S.-person status or another valid exception. The IRS treaty list does not include Taiwan as of this review, so a person residing in Taiwan should not assume treaty-rate relief. Professional analysis is essential.
Put the guide to work
Create a cross-border file that both tax teams can use
Keep one shared timeline and document set for both jurisdictions: travel, work location, payroll, awards, account ownership, maximum values, income and taxes paid. The financial plan can organize cash and investments, while U.S. and Taiwan professionals decide filing, reporting and legal treatment.
Use the sequence below as preparation, not as individualized advice. Current TSMC documents control employer benefits, and qualified tax or legal professionals should confirm decisions in their areas.
- Determine federal and Arizona residency from documented facts
- Map compensation to work locations and vesting periods
- Inventory foreign accounts and specified foreign assets
- Identify who prepares each return and information form
- Review transfers, sales and retirement distributions before they occur
- Taiwan bank and brokerage accounts
- Foreign funds and individual securities
- Pension or labor-retirement interests
- Insurance with cash value
Frequently asked questions
Questions employees ask next
Does working for TSMC in Arizona automatically make me a U.S. tax resident?
No single employment fact answers residency. Immigration status, days present and applicable elections or exceptions matter.
Do Taiwan accounts have to be reported in the United States?
U.S. persons may have FBAR, Form 8938 or other reporting. A cross-border tax professional should review the complete inventory.
Can I keep a U.S. 401(k) after returning to Taiwan?
Often an account can remain when plan rules permit, but provider policy, tax status and future distribution withholding require review.
Primary sources
What this guide is based on
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