OMTs may also choose to assess the BOS impact through an evaluation. Given the annual monitoring and review step, conducting an evaluation is not a mandatory step of the BOS but it might be helpful to do a multi-year evaluation of the BOS to guide OMTs through the review process.
A BOS evaluation should focus on the relevance, efficiency, effectiveness, and sustainability as defined by the UN Evaluation Group (UNEG)[1]. A sample structure of an evaluation with guiding questions is available in Annex 5.
[1] UNEG Norms for Evaluation in the UN System, www.unevaluation.org