25 U.S.C. § 1621s

The Service shall respond to a notification of a claim by a provider of a contract care service with either an individual purchase order or a denial of the claim within 5 working days after the receipt of such notification.

If the Service fails to respond to a notification of a claim in accordance with subsection (a), the Service shall accept as valid the claim submitted by the provider of a contract care service.

The Service shall pay a completed contract care service claim within 30 days after completion of the claim.