In a footnote in Kirsty Gover's Tribal Constitutionalism (p 122), citing an interview with genealogist Rita Souther, the author notes that N.E. stood for Not Eligible:
Some base rolls exclude non-Indians recorded on the basic roll, for
instance by identifying those recorded as 'N.E.', or 'Not Eligible',
indicating that the person was deemed to not be eligible for
However, Gover adds that according to Mary Frances Morrow article on BIA Indian Census Rolls, she has explained that N.E. stood for Not Enrolled:
It was considered helpful to indicate the number for the person on the previous year's census. Persons also could be designated by a number peculiar to that reservation, if it was explained somewhere, or they could be listed as "N.E.", or “Not Enrolled.” In the 1930s, sometimes only supplemental rolls showing the additions and deletions from the previous year were submitted.
I am inclined to agree with Morrow that it was meant to stand for Not Enrolled, as I can find several examples from other Indian census rolls where the words "Not enrolled" are included in the absence of any number. For example, this 1925 census roll for the Chippewa Indians shows:
It is always worth looking at the instructions given to the enumerator. In this case they can be found near the start of the film. Unfortunately the abbreviation 'N.E.' is not mentioned, but the first instruction is suggestive that it may stand for Not Enrolled:
(A) A separate roll is to be made of each reservation; also, of each rancheria or reserve, and a separate roll of Indians allotted on the public domain or homesteading. The roll is to be based on enrollment and not on residence.
Though it appears not to be relevant in this case, it is also worth adding that my first thought was that N.E. might be the initials of the person who made the ammendment. In my experience with English records, when a change or correction was made on (for example) a birth or baptism certificate, the vicar or registrar would often initial the correction.