Overview

Nonresident aliens and dual‑status aliens have distinct federal filing obligations under U.S. tax law. The rules determine which income is taxable, which forms to file, and the deadlines you must meet. Residency status is the key: it controls whether you are taxed on U.S. source income only (nonresident) or on worldwide income (resident). When your status changes during the year, you may be a dual‑status alien and must follow special filing rules.

This article summarizes the residency tests, required forms, common traps, tax‑treaty considerations, deadlines, and practical steps to stay compliant. Recommendations and examples reflect industry‑standard guidance (IRS Publication 519) and professional practice through 2025. This content is educational and not individualized tax advice — consult a tax professional for your facts and circumstances.

Sources: IRS — Nonresident Alien General Information; IRS — Dual‑Status Aliens; IRS Publication 519 (U.S. Tax Guide for Aliens).

How residency is determined

U.S. tax residency is decided by two main tests:

  • Green Card Test: You are a U.S. resident for tax purposes if at any time during the calendar year you were a lawful permanent resident (held a green card).
  • Substantial Presence Test (SPT): You meet the SPT if the sum of days present in the U.S. equals 183 or more, calculated as: days in current year + 1/3 of days in previous year + 1/6 of days in the year before that. Certain days may be excluded (e.g., substantial exemptions for some exempt individuals and days of transit).

If you meet neither test, you are generally a nonresident alien. If you meet one of the tests for part of the year and not for the remainder, you may be a dual‑status alien for that tax year.

(See IRS Publication 519 for details and exceptions.)

Who files which forms

  • Nonresident alien (NR): Generally files Form 1040‑NR to report U.S. source income and compute tax. You may also need Form 8843 to explain days claimed as exempt for SPT. If claiming exemption from withholding on compensation for personal services, Form 8233 may be used by certain nonresident aliens to claim treaty benefits or a withholding exemption.

  • Dual‑status alien: Files a dual‑status return — usually a Form 1040 (or 1040‑SR) for the resident part of the year and a Form 1040‑NR for the nonresident part. Dual‑status returns cannot use the married filing jointly status (with limited exceptions) and typically need a statement attached describing the residency transition and allocating income to resident and nonresident periods.

  • Resident for the whole year: Files Form 1040 and reports worldwide income.

For practical how‑to guidance on Form 1040‑NR and common withholding scenarios, FinHelp has detailed glossaries such as the Form 1040‑NR guide and an article on federal withholding rules for nonresident aliens: Form 1040‑NR — U.S. Nonresident Alien Income Tax Return and How Federal Withholding Rules Affect Nonresident Aliens.

What income is taxed

  • Nonresident alien: Taxed on U.S. source income (wages for services performed in the U.S., fixed or determinable annual or periodical (FDAP) income such as interest, dividends, rents) and certain effectively connected income with a U.S. trade or business. Nonresident aliens generally are not taxed on foreign source income.

  • Dual‑status alien: Taxed as a resident for the resident portion of the year (worldwide income is includible) and as a nonresident for the nonresident portion (U.S. source income only). You must allocate income and deductions between the two periods.

Note: Tax treaty provisions may alter what income is taxable or the applicable rates. If relying on a treaty position, follow IRS guidance on claiming treaty benefits and attach required documentation to your return.

Deadlines and extensions

  • Typical deadlines: If you are a nonresident alien who received wages subject to U.S. income tax withholding, your Form 1040‑NR is generally due by April 15 (the regular individual due date) of the following year. If you are a nonresident who did not receive wages subject to withholding, the due date is typically June 15. Dual‑status returns generally follow the same calendar but have special filing rules for the resident portion and the nonresident portion.

  • Extensions: You can request an extension to file, but an extension to file is not an extension to pay. If you expect tax due, pay by the original deadline to avoid penalties and interest. See IRS guidance for specific filing and payment dates.

(Always confirm current year deadlines at the IRS website or with a tax professional.)

Residency change (example)

In my practice I see clients who arrive on work visas and later acquire a green card in the same calendar year. For example, a software engineer who worked in the U.S. from January through July as a nonresident (taxed only on U.S. source wages) and received a green card in August becomes a dual‑status alien. They must:

  1. File Form 1040‑NR for the nonresident period, reporting U.S. source income earned while nonresident.
  2. File Form 1040 for the resident period, reporting worldwide income for that period.
  3. Attach a statement that identifies the date of residency change and how income is allocated.

These steps can affect deductions, exemptions, and eligibility for credits. Careful recordkeeping of arrival and departure dates, visa changes, and pay statements simplifies the process.

Common mistakes and how to avoid them

  • Misclassifying residency: Run the SPT calculation and review green card status yearly. Small errors in day counts can change tax liability materially.
  • Ignoring treaty benefits: Many taxpayers leave money on the table by not checking whether a tax treaty with their home country reduces withholding or exempts income.
  • Missing Form 8843: Certain exempt individuals (students, trainees) must file Form 8843 even with no income to preserve nonresident status for SPT purposes.
  • Improper dual‑status filing: Dual‑status returns have unique rules (e.g., limits on standard deduction, generally cannot file joint returns). Use Publication 519 as a checklist.

Recordkeeping checklist

  • Passport entry/exit stamps and travel logs (dates present in U.S.).
  • Visa/green card documents and change‑of‑status notices.
  • Pay stubs, W‑2s, 1099s, and documentation of foreign income.
  • Copies of any treaty claims, Forms 8233, W‑8BEN (if applicable), and correspondence with employers.
  • Filed Forms 8843, 1040‑NR, 1040, and supporting schedules.

State tax considerations

State residency rules differ from federal rules. Even if you are a nonresident for federal purposes, you may owe state income tax on income sourced to that state. Check state guidance or consult a preparer familiar with both federal and state residency rules. FinHelp’s state residency and withholding pages provide additional context, for example the article on state residency rules.

ITINs, SSNs and filing mechanics

Nonresident aliens who cannot obtain an SSN must apply for an Individual Taxpayer Identification Number (ITIN) using Form W‑7. Submit supporting documents or use an IRS‑authorized acceptance agent. If you are eligible for an SSN (for example, because you have work authorization), apply through the Social Security Administration.

If you claim treaty benefits that reduce withholding, present your employer with the appropriate form (often Form 8233 for certain independent personal services or a W‑8 series form for foreign entities) and keep copies.

Penalties and audits

Failing to file or filing incorrectly can result in penalties, interest, and in some cases collection actions. Dual‑status years can trigger IRS scrutiny when income allocations, treaty claims, or residency dates seem inconsistent. Maintain documentation and consult a preparer with international tax experience when filings are complex.

Practical tips

  • Start with a residency test spreadsheet: automatically compute day counts for the SPT and flag years where residency changes. This reduces classification errors.
  • Keep travel evidence: airline itineraries and passport stamps are often the most defensible records of presence in the U.S.
  • When in doubt, attach a clear statement to the return explaining residency status, the date of change, and items being reported for each period.
  • Use authoritative sources: IRS Publication 519 and the IRS pages on nonresident and dual‑status aliens are primary references (see links below).

When to get professional help

Engage a tax professional if you:

  • Have income in multiple countries and potential credit or deduction issues.
  • Changed immigration status (e.g., visa to green card) within the tax year.
  • Plan to claim treaty benefits or need to navigate Form 8233 withholding exemptions.

In my experience advising cross‑border clients, early coordination between employers, payroll, and tax advisors reduces withholding surprises and filing complexity.

Useful links and references

Internal FinHelp resources:

Disclaimer

This article provides general information based on IRS guidance and professional practice through 2025. It does not constitute legal, tax, or accounting advice for any individual. For tailored guidance, consult a licensed tax professional or attorney who can evaluate your specific facts.