Tax Implications of 10-Year B2 Travel Visa?

I didn't see an answer to this query so I'll take a whack at it.

There are two things that matter to someone who is not a lawful permanent resident (hold a green card) of the U.S.:

1. Do they have any U.S. source income?
2. Physical presence in the U.S.

If the person remains a nonresident alien(fails the substantial presence test.... and while I am on this subject, it is not staying under 183 days. More later.) then only U.S. source income could be subject to U.S. tax. If the person becomes a resident alien under the substantial presence test) then all income could be subject to U.S. tax. The substantial presence test looks at your physical presence over 3 years: CY, CY - 1, & CY - 2. To pass you must have at least 31 days of presence in the CY and 183 days of physical presence over the 3 year period. You count all days in the current year (CY), plus 1/3 of the days in CY - 1 plus 1/6 days in CY - 2. There are special rules for those who are dual-status aliens, first year of residency, last year of residency, first year choice and electing to be treated as a resident if you are married to a resident or citizen of the U.S.

Notice, that I did not mention "visa". These rules apply regardless of whether you are present lawfully or unlawfully in the U.S with a couple of exceptions. Holders of certain visas will be considered to be a nonresident alien regardless of the number of the days of physical presence. These persons are generally students, teachers, researchers and scholars holding either an F, J, M or Q type visa. These persons are known as exempt individuals: meaning they are exempt from the substantial presence test for a certain period of time; not exempt from taxes on US source income. Professional athletes temporarily in the US are also exempt. I don't know what type of visa they have.

So... someone holding a B type of visa is not an exempt individual and would be considered a nonresident alien unless they meet the substantial presence test.

Please note that there is even an exception to the substantial presence test if you can show what is known as a "closer connection to a foreign country."

For more details on who is a resident or nonresident, sources of income, how aliens are taxed, exceptions and/or exclusions due to a tax treaty and other subjects see IRS Pub 519, Tax Guide for Aliens.