34 Tex. Admin. Code § 25.33
Contributions and other additions with respect to a participant, including payments for the purchase of TRS service credit, may not exceed the limitations of 26 United States Code §415. Payments for the purchase of TRS service credit may be limited under §415 to a percentage of compensation of the participant from the employer for the plan year in which the payments are sought to be made. Payments made by a beneficiary in order to purchase service credit after the death of a member are subject to the same limitations as if the payments were made by the member. For a plan year in which no compensation is received by a member from a TRS-covered employer, the member or the member's beneficiary may not make deposits for service credit, unless such deposits specifically would be permitted under §415. TRS shall administer the requirements for limitations on contributions and other additions in a manner necessary to comply with federal tax laws relating to plan qualification.
34 Tex. Admin. Code § 25.33