this is from the k-3 instructions. hope it helps
Column (f). Sourced by partner. You must determine the source and separate category of the income reported in this column. The income in this column will generally be with respect to sale of personal property other than inventory, depreciable property, and certain intangible property sourced under section 865. This column might also include foreign currency gain on a section 988 transaction. If you are a U.S. citizen or resident, sales and gains reported in this column will generally be U.S. source income and not reported on Form 1116 or 1118 unless you elect to re-source such income under an applicable income
tax treaty. There are certain exceptions, for example, a U.S. citizen or resident with a tax home (as defined in section 911(d)(3)) in another country is treated as a nonresident if an income tax of at least 10% is imposed by and paid to a foreign country regarding such sale. See the instructions for Part I, box 1, above. Also, the source of foreign currency gain or loss on section 988 transactions may be determined by reference to the residence of the QBU on whose books the asset, liability, or item of income or expense is properly reflected. See the Instructions for Form 1118 and Pub. 514 for additional details.
