Publication 598
taxmap/pubs/p598-010.htm#en_us_publink100067581The unrelated business taxable income of a foreign organization
exempt from tax under section 501(a) consists of the organization's:
- Unrelated business taxable income derived from sources within
the United States but not effectively connected with the conduct of a trade or
business within the United States, and
- Unrelated business taxable income effectively connected with
the conduct of a trade or business within the United States, whether or not this
income is derived from sources within the United States.
To determine whether income realized by a foreign organization
is derived from sources within the United States or is effectively connected
with the conduct of a trade or business within the United States, see sections
861 through 865 and the related regulations.