Safe Home Act of 2021 This bill makes unregulated custody transfers a form of child abuse and neglect under federal child-welfare law. Specifically, an unregulated custody transfer occurs when a child is placed with a non-relative or otherwise unfamiliar adult, with the intention of severing the parental or guardian relationship with the child, without reasonably ensuring the child's safety, and without legally transferring parental or guardian rights. The bill also requires the Department of Health and Human Services to (1) report on the causes, effects, and prevalence of unregulated custody transfers; (2) develop policy recommendations for preventing such transfers; and (3) issue guidance to the states.