(1) Nonresidents and part-year residents are subject to the same filing requirements as residents unless otherwise expressly exempted in statute.

(2) Part-year residents and nonresidents must include all Montana source income on Schedule III. Montana source income is defined in 15-30-101 , MCA.

(3) Part-year residents and nonresidents must complete Schedule IV and compute their tax liability by the tax determined as if they were a resident by the ratio of their Montana source income to income from all sources.

(4) Nonresident estates and trusts are subject to the same filing requirements set forth in (1) through (3) unless otherwise expressly exempted in statute.