The Moss-PAS (ChA), formerly called ChA-PAS Interview, is for the mental health assessment of children and adolescents across the full developmental spectrum, including intellectual disability. It provides a semi-structured interview format in which the young person may contribute to whatever degree they are able, or it may be conducted by informant interview only. Recently revised and fully compliant with DSM5 and ICD11, the scoring system provides a single score for each of the diagnostic constellations, each of which has a corresponding threshold. If the child or young person reaches or exceeds the threshold, it is probable that they warrant a diagnosis in that constellation. However, a strong emphasis is placed on the importance of expert clinical judgement when interpreting the scores in relation to other pieces of information, such as history, environment, and family factors. Question wordings, symptom definitions, and glossary notes were developed by clinical experts from Canada and the UK.