This study aimed to examine the practice of psychiatrists in a large learning disability service in recording capacity to consent to treatment and side effect discussion, and the impact of measures aimed at improving this. Three audit cycles were completed between 2007 and 2009, each examining 26 case notes selected at random. Information was gathered on recording of capacity and documentation of explanation of potential side effects. Changes in practice following the introduction of a rubber stamp in 2008, as a visual prompt for clinicians, were examined. Rates of recording of capacity rose from 30% in 2007 to 51% in 2009 (P = 0.000006). Capacity was more likely to have been recorded if the stamp was present (odds ratio 13.5, p < 0.0001). Recording of side effect discussion was consistently higher than that of capacity and showed little change between cycles. We conclude that the use of a rubber stamp in case notes was associated with improvements in the recording of capacity assessments.