(1) Any income derived from sources within the boundaries of federally recognized Indian country in Oregon by any enrolled member of a federally recognized American Indian tribe residing in federally recognized Indian country in Oregon at the time the income is earned is exempt from tax under this chapter.
(2) An extract from the tribal rolls or other documentary proof of the taxpayer’s enrolled status and other additional proofs as may be required by the Department of Revenue, shall be attached to or accompany any return for any year for which exemption under subsection (1) of this section is claimed. The requirement of proof may be waived partially, conditionally or absolutely, as provided under ORS 315.063.