Tex. Finance Code § 345.079: ALLOCATION OF PAYMENTS ON CONSOLIDATION OF CONTRACTS.

(a) If a subsequent purchase is consolidated with a contract and the retail seller retains title or takes a security interest, including a lien, in any of the goods purchased under one of the contracts:

(1) the total of all payments made before the subsequent purchase is considered to have been applied to the previous purchases; and

(2) each payment made on the consolidated contract after the subsequent purchase is considered to be allocated to each purchase in the same ratio as the original cash price of the purchase bears to the total of the original cash prices of all purchases under the contract.

(b) All of a down payment on a subsequent purchase shall be allocated to that purchase.

(c) If the amount of installment payments is increased after a subsequent purchase, the retail seller may elect to allocate:

(1) an amount of the payment equal to the original periodic payment to the previous purchase; and

(2) the remainder of the payment to the subsequent purchase.

(d) This section does not apply if the previous and subsequent purchases involve:

(1) goods, including equipment or parts, attached or affixed to goods previously purchased and for which full payment has not been made; or

(2) services rendered by the retail seller at the retail buyer's request in connection with goods described by Subdivision (1).

Acts 1997, 75th Leg., ch. 1008, Sec. 1, eff. Sept. 1, 1997.