Montana Title 33. Insurance and Insurance Companies § 33-32-108. Retroactive denials prohibited

When prior approval for a covered service is required and obtained by or on behalf of a covered person and the covered person undergoes the covered service, the approval is final and the health insurance issuer may not rescind approval after the covered service has been provided.  This section does not apply to cases of fraud, misrepresentation, nonpayment of premium, exhaustion of benefits, if the covered person for whom the prior approval was granted is not covered when the service was provided, or if the covered service provided was not the same covered service that received prior approval, unless it was necessary and incidental.