AbstractInvestigating individual level-Indigenous identification change by Aboriginal and Torres Strait Islander Australians has been enabled through the linkage of census data across time. This study focusses on the population who moved from an identification of Indigenous in the 2011 census to not Indigenous in the 2016 census. We calculated transition probabilities for a range of personal characteristics to investigate the influence of broad life-course transitions on the pattern of identification change. In addition to age, we found that sex, employment, mixed ancestry, interstate migration, and living arrangements had the strongest associations with the risk of a transition to not Indigenous. The highest transition probabilities were at each end of the adult life-course and the role of “not stated” was implicated, destabilising assumptions that decisions to identify as Indigenous, or not, always reflect personal agency. Finally, the paper challenges the adequacy of an origin-based identity question to define the increasingly complex ethnic histories of Aboriginal and/or Torres Strait Islander people. Both improved definition and enumeration of Indigenous Australians are fundamental to current national conversations about constitutional recognition and continuing gaps in measured health and wellbeing.