As outlined in ABF Information Paper Number 1, a critical element of Activity Based Funding (ABF) is the need to define, classify, count, cost and pay for each health care activity in a consistent manner. For acute patients who stay in hospital for more than a day, this is not an issue. These patients are classified as acute 'overnight admitted patients' and are counted by Diagnosis Related Group (DRG). However, the definitions and counting rules are not consistent for patients who receive treatment and then go home on the same day ('same day' patients). The main focus of this paper is to highlight the issues faced when classifying the activity of these 'same day' patients.