Foster care and Guardianship are not synonyms. Foster care often includes care payments, and that results in a 1099 being issued. For Foster care examples, your residence will be evaluated, there will be an official agency between you and that child at all times, and you need permission to even take them out of town/State/County. Guardianship and custody are not synonyms, either. There can be legal custody that is not physical custody. But this is not tax regulation; this is child welfare.