This award will support a two-day Virtual NSF Project Scoping Workshop on the topic of "Precise and Accurate Calculations of Neutrinoless Double-Beta Decay". Theoretical nuclear physics input is critical to the interpretation of experimental results that could demonstrate that neutrinos are their own antiparticles. As such, theoretical nuclear physics will play an important role in understanding the excess of matter over antimatter in the universe, one of outstanding grand challenges in modern science. This Project Scoping Workshop will provide a forum for the community of practitioners in this field to take stock of recent scientific advancements, identify current challenges, discuss opportunities to overcome those challenges, and map a way forward for the success of the experimental Neutrinoless Double-Beta Decay projects. This project advances the goals outlined out in the 2015 LONG RANGE PLAN for NUCLEAR SCIENCE regarding “the timely development and deployment of a U.S.-led ton-scale neutrinoless double beta decay experiment.”<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.