Insurance lawyers know to look at the Texas Insurance Code, starting at Section 1952.101, to see the requirement that insurance companies are required by the Texas Department of Insurance and by statute to provide underinsured (UIM) coverage in their automobile polices.
One of the steps an insurance lawyer is suppose to make when trying to collect UIM benefits is to get written permission from the UIM insurance carrier to settle with the responsible third party before actually settling the case with the responsible third party. This is required so as to not prejudice the right of the insurance carrier to subrogate against the third party in the appropriate situation.
This issue is discussed in a 2019, opinion from the Dallas Court of Appeals. It is styled, Curtis Davis v. State Farm Lloyds, Inc.