Drawing on the expertise of public international law and tax experts, this report explores the technical feasibility to develop a multilateral instrument to modify tax treaties so as to efficiently implement the tax treaty-related BEPS measures. The report concludes that such an instrument is desirable and feasible and that negotiations for the multilateral instrument should be convened quickly. Based on this analysis, a mandate has been developed for an ad-hoc group, open to the participation of all countries on an equal footing, to develop the multilateral instrument and open it for signature in 2016.