Currently, we do not know the exact number of people with autism spectrum disorder (ASD) living in Scotland. This project sets out to explore this issue further by building on existing eSAY datasets held by the Scottish Consortium for Learning Disability. As these datasets currently include only certain information on people with autism due to the methodology used, they merely begin to capture the subset of the population known to learning disability services. Therefore, they provide an under-estimate of the number of people with autism in Scotland. This is due to system difficulties and inconsistencies in recording ASD diagnoses. Furthermore, people on the autism spectrum may not always receive services, and those who do, may not receive services from local authorities, but rather from health services. Thus the difficulty in identifying this population lies in the wide diversity of services used by people on the spectrum with levels of unmet needs present making this more problematic. Furthermore, people with ASD often remain undiagnosed making identifying them harder. The uncertainty around the number of people with ASD in Scotland makes it challenging to plan, design and deliver transition services, which would be appropriate, person-centred and enabling.