42 CFR §433.152

1. (a)Except as specified in paragraph (b) of this section, the State agency may develop the specific terms of cooperative agreements with other agencies as it determines appropriate for individual circumstances.
2. (b)Agreements with title IV-D agencies must specify that:
   1. (1)The Medicaid agency may not refer a case for medical support enforcement when the following criteria have been met:
      1. (i)The Medicaid referral is based solely upon health care services provided through an Indian Health Program (as defined at 25 U.S.C. 1603(12)), including through the Purchased/Referred Care program, to a child who is eligible for health care services from the Indian Health Service (IHS).
      2. (ii)[Reserved]
   2. (2)The Medicaid agency will provide reimbursement to the IV-D agency only for those child support services performed that are not reimbursable by the Office of Child Support Enforcement under title IV-D of the Act and that are necessary for the collection of amounts for the Medicaid program.