Purpose The purpose of this paper is to evaluate whether two regional intellectual disability (ID) assessment and treatment (A&T) units in England were meeting the recommended length of stay stipulated by the Learning Disability Professional Senate, in line with the Transforming Care (TC) agenda. A secondary purpose of the study was to evaluate the reasons for admissions and delayed discharges in order to inform how to reduce these. Design/methodology/approach A retrospective evaluation of 85 admissions across two A&T units was conducted over a three-year period (2013–2016) following publication of the TC agenda. Findings There were 85 admissions compared to 71 discharges. Of the 85 admissions, 11 were readmissions. The most common factors thought necessary to prevent admission were early support for care providers or alternative service provision. There were barriers to discharge in over half of admissions; the main reason was a lack of suitable service provision. Practical implications The study suggests that providing specific support or training to care providers could prevent (re)admission and ensure shorter admissions. Further research to establish reasons for the reported lack of suitable providers would be beneficial. Originality/value This study provides current admission and discharge rates for regional A&T units, as recommended by the TC national guidance. It also provides potential reasons underlying preventable admissions and delayed discharges and therefore indicates what might be necessary to prevent admissions and reduce the length of inpatient stays for people with ID and/or autism.