There is growing research interest in autism-related sex differences. Many behavioural and cognitive sex differences have been identified, with implications for research and clinical practice. Much of this research has relied on self-report autism measures, which are assumed to measure autistic traits equally in males and females. However, robust evidence for this assumption is lacking. Previous findings have not been replicated and no study has directly compared sex differences across multiple self-report autism measures in the same sample. To address this gap in research, a large sample of adults (N = 1000, 500 female) will complete a series of self-report autism measures. Following descriptive analyses, we will investigate the measurement invariance by sex of each measure. We thereby aim to improve understanding of which self-report autism measures, if any, are optimal for testing autism-related sex differences in future research.