In some instances, the start and end dates of interventions may not be definitive, or your intervention may be ongoing. If people access your intervention in a staggered fashion (coming and going at different times), you can survey individuals as they sign up and again when they leave (whether that be days, weeks or months later). If your engagement with people is on an ongoing basis, then you can survey annually or semi-annually. If adopting this approach, you will be able to measure change and attach value on an annual basis. Whether you survey annually or semi-annually, you should report on social value annually to mirror your financial report.