This guidance document provides recommendations for nonclinical testing and study design considerations for Investigational Device Exemptions (IDEs) feasibility and pivotal clinical studies for implanted Brain-Computer Interface (BCI) devices for patients with paralysis or amputation. The field of implanted BCI devices is progressing rapidly from fundamental neuroscience discoveries to translational applications and market access. Implanted BCI devices have the potential to bring benefit to people with severe disabilities by increasing their ability to interact with their environment, and consequently, providing new independence in daily life. For the purposes of this guidance document, implanted BCI devices are neuroprostheses that interface with the central or peripheral nervous system to restore lost motor and/or sensory capabilities in patients with paralysis or amputation.