Substantial Presence Test

The substantial presence test is the IRS day-count rule that decides whether a foreign individual is a US resident alien for tax purposes. Resident aliens are taxed like US citizens on worldwide income. Nonresident aliens are taxed only on US-source income under a separate regime. For a US company paying a foreign contractor, the test is the dividing line between two completely different documentation and reporting paths. The IRS sets out the rule on its Substantial Presence Test page.

The Day Counts

The IRS states that an individual is considered a US resident for tax purposes if physically present in the US on at least “31 days during the current year, and 183 days during the 3-year period that includes the current year and the 2 years immediately before that” (IRS Substantial Presence Test).

The 183-day figure is not a simple sum. The IRS counts:

1. All the days the individual was present in the current year, and
2. One-third of the days present in the first year before the current year, and
3. One-sixth of the days present in the second year before the current year.

So a person who spent 120 days in the US in each of three years counts 120, plus 40 (one-third of 120), plus 20 (one-sixth of 120), for a weighted total of 180. That is below 183, so the person does not meet the test for the current year even though they spent 360 actual days in the US across the period. The weighting is what makes the test easy to misread.

Why It Matters to a US Payer

The test result selects the tax form a contractor must provide before payment.

• Resident alien. A foreign individual who meets the substantial presence test is a US resident alien. They complete Form W-9 like a US person, and the payer reports payments the same way it reports payments to any US contractor.
• Nonresident alien. A foreign individual who does not meet the test is a nonresident alien. They complete Form W-8BEN, and the payment falls under nonresident alien withholding, with a default 30 percent rate on US-source income unless a treaty reduces it.

Collecting the wrong form means the payer applies the wrong withholding and files the wrong year-end return. A W-9 from someone who is actually a nonresident alien can leave required withholding uncollected, and the payer carries personal liability for tax it should have withheld.

Days That Do Not Count

Not every day of physical presence counts toward the 183-day total. The IRS excludes, among others, days a regular commuter travels from Canada or Mexico, days in transit between two foreign locations, and days an “exempt individual” such as certain teachers, students, and foreign-government-related individuals is present. These exclusions can pull the weighted total below 183 even after a long US stay, which is why the determination depends on facts the payer cannot guess from a head count.

Related Terms

• NRA Withholding: the regime that applies when an individual is a nonresident alien.
• Form W-8BEN: the form a nonresident alien gives the payer.
• Tax Residency Certificate: documentation of residency in a treaty country.

Omnivoo Contract Management collects the correct tax form from each foreign contractor, sorts resident aliens from nonresident aliens, and applies the right withholding and year-end reporting for each.