34 Tex. Admin. Code § 25.188
A beneficiary who elects to complete installment payments under the Government Code, § 825.410(d)(2), may complete payment only for the same type of service credit for which the member had made at least one payment prior to the member's death. If the member had elected to make installment payments on fewer years of service credit than he was eligible to purchase, the beneficiary may complete the installment payments only for the years of credit elected by the member and for which the member had made at least one payment. A beneficiary who elects to complete installment payments must do so in a single lump sum payment received by TRS no later than 12 months after the date of death of the member. Payments for TRS service credit shall be paid in a manner consistent with any applicable limitations on contributions under 26 United States Code §415, including any applicable limitations on payments as a percentage of compensation of the participant from the employer for the school year in which the payments are sought to be made by a beneficiary. A beneficiary may not purchase TRS service credit under this section if payments exceed applicable limitations on contributions.
34 Tex. Admin. Code § 25.188