Impact is often defined simply as the differences made as a result of the organisation's activity.
Measuring impact is increasingly important for organisations. Boards should be able to show the difference the work of their organisation is making. This is important in relation to being able to demonstrate Public Benefit if the organisation is a charity as well as in providing accountability to stakeholders and beneficiaries. More broadly, it is important to show value for money in the way the organisation is using its assets, to show that it is meeting its organisational puposes as effectively as possible.
Impacts can be intentional and unintentional and they can be positive or negative, organisations seeking to measure their impact should be aware of all of the possible impacts they are having. Often impact can be subtle and therefore more difficult to see and quanitfy. They can also be short term and long term which will mean that different approaches may be needed to record and measure them.
More information on measuring impact is available from Inspiring Impact NI website which has links to a wide range of tools to assist organisations to measure impact.
Also of interest may be the Volunteering Impact Assessment Toolkit.