Step by step description of using the CANDID-S as a needs assessment tool is provided. This includes suggestions on what CANDID-S can be used for (clinical and research purposes in community and hospital settings) and who can use CANDID-S (no formal training is required and can be used by any person with experience in working with adults with intellectual disabilities and mental health problems). Furthermore, the question of who should be interviewed is addressed, whilst highlighting the importance of assessing needs of the person from three perspectives that of the person being assessed, their informal carer and that of staff involved in their care. Then a description is provided as to how the instrument is used by way of a semi-structured interview using trigger questions in each domain, to initiate discussion. A timeframe of 4 weeks is used and the interview with each respondent takes typically 10-15 minutes. Finally, the approach to recording the need ratings is descibed and the concept of summary scores is introduced.