28 Tex. Admin. Code § 21.4001
This subchapter applies to group preferred provider benefit plans and evidences of coverage issued pursuant to Insurance Code Chapters 843 and 1301. The subchapter outlines a group policyholder's or group contract holder's liability for premium payment, and a health carrier's obligation to provide coverage, from the time an individual insured or enrollee loses eligibility for coverage as part of a particular group until the end of the month in which the group policyholder or group contract holder notifies the health carrier that the individual is no longer part of the group eligible for coverage. The subchapter does not impose requirements on a group policyholder, a group contract holder, or a health carrier when an entire group ends coverage under a health benefit plan or when an individual terminates coverage while remaining part of the group eligible for coverage.
28 Tex. Admin. Code § 21.4001