Ariz. Rev. Stat. § 20-1407
A group hospital or medical expense insurance policy delivered or issued for delivery in this state more than one hundred twenty days after August 27, 1977 that provides that coverage of a dependent child of an employee or other member of the covered group shall terminate on attainment of the limiting age for dependent children specified in the policy, shall also provide in substance that attainment of such limiting age shall not operate to terminate the coverage of that child while the child is and continues to be both incapable of self-sustaining employment by reason of intellectual disability or physical disability and chiefly dependent on the employee or member for support and maintenance. Proof of such incapacity and dependency shall be furnished to the insurer by the employee or member within thirty-one days of the child's attainment of the limiting age and subsequently as may be required by the insurer, but not more frequently than annually after the two-year period following the child's attainment of the limiting age.
A.R.S. § 20-1407