The NeXUS facility welcomes proposals from the whole scientific community. Researchers from inside or outside of the United States are welcome to submit proposals. 

A proposal for facility time must be submitted by the Principal Investigator (PI) for the proposed project. The PI is responsible for:​

1. Overseeing the planning, preparation, and administration of the project.​
2. Ensuring all resources committed to in the proposal are provided to support the project.​
3. Working with NeXUS staff to execute the project, mitigate risks that arise, and resolve any project issues that arise.​
4. Reporting project outcomes to NeXUS.

User projects are assumed to be for fundamental research purposes, and NeXUS expects that results will be disclosed in user publications. However, users can propose and conduct non-fundamental projects that collect proprietary or commercial data. The PI must inform NeXUS prior to proposal submission if they are proposing a non-fundamental project, and NeXUS reserves the right to charge usage fees for these projects.​

Proposals will be evaluated and recommended by an independent, external review panel of scientific experts. Criteria for selection will include technical merit, broader impacts, feasibility, and safety.  NeXUS may specify additional, call-specific criteria and will publicize these in the announcement of each call. Recommended experiments will be prioritized for system time based primarily on their external evaluation and secondarily to ensure NeXUS makes efficient use of its resources to achieve its mission of scientific and societal impact. A list of awarded experiments, naming the PI and sharing the title, will be made public once scheduling is complete.​