Adults are increasingly self-identifying as autistic, and reporting problems being referred for an autism diagnostic assessment. This scoping review aims to ascertain: (1) what research has been conducted on the self-identification process of autism in adults, who do and do not have a formal diagnosis of autism, and (2) which aspects of the self-identification process could be used to improve the referral and the diagnostic process of an adult autism assessment. The main themes identified were: the diagnostic process from a client's perspective; the process of self-identifying as autistic from a lifespan perspective; an autistic identity; sexual identity and experiences, and the perception of autism as a difference or a disability. These themes could positively enhance the referral and diagnostic process.