Through funding programmes such as Trade Up and the Community Business Fund, Power to Change supports community businesses to trade for the benefit of their local community; yet how can we understand the financial impact that Power to Change has had on community businesses? The answer is not straightforward, and programme impact can be difficult to isolate amongst a range of activities undertaken over a multi-year period by numerous community businesses. In response to such a challenge, MyCake and Renaisi developed a data reporting approach to better understand the financial impact of funding and investment programmes on community businesses (and other trading organisations) – and called this the ‘Year Zero reporting approach’. This paper explains what the Year Zero reporting approach is and why it is beneficial, and gives practical examples of its applications on the Community Business Fund and Trade Up programmes. It also provides guidance to funders and evaluators to decide whether this approach would be appropriate for other funding programmes going forward.