Allows Medicare to cover and code services furnished by defined "advanced psychology trainees" under general supervision, requires HHS to create a billing modifier to identify those trainee‑provided services, and takes effect one year after enactment. Requires HHS to issue guidance to States within one year to help remove Medicaid and CHIP barriers to coverage of services furnished by these trainees, including recommended billing codes, legal mechanisms (such as waivers), and examples of successful State approaches.