(1) If, in a retail installment transaction, a retail buyer makes any subsequent purchases of goods or services from a retail seller from whom he or she has previously purchased goods or services under one or more retail installment contracts, and the amounts under such previous contract or contracts have not been fully paid, the subsequent purchases may, at the seller's option, be included in and consolidated with one or more of the previous contracts. All the provisions of this chapter with respect to retail installment contracts shall be applicable to such subsequent purchases except as hereinafter stated in this subsection. In the event of such consolidation, in lieu of the buyer's executing a retail installment contract respecting each subsequent purchase, as provided in this section, it shall be sufficient if the seller shall prepare a written memorandum of each such subsequent purchase, in which case the provisions of RCW 63.14.020, 63.14.030, and 63.14.040 shall not be applicable. Unless previously furnished in writing to the buyer by the seller, by sales slip, memoranda, or otherwise, such memorandum shall set forth with respect to each subsequent purchase items (a) to (h) inclusive of RCW 63.14.040(1), and in addition, if the service charge is stated as a dollar amount, the amount of the time balance owed by the buyer to the seller for the subsequent purchase, the outstanding balance of the previous contract or contracts, the consolidated time balance, and the revised installments applicable to the consolidated time balance, if any, in accordance with RCW 63.14.040. If the service charge is not stated in a dollar amount, in addition to the items (a) to (h) inclusive of RCW 63.14.040(1), the memorandum shall set forth the outstanding balance of the previous contract or contracts, the consolidated outstanding balance, and the revised installments applicable to the consolidated outstanding balance, in accordance with RCW 63.14.040.

The seller shall deliver to the buyer a copy of such memorandum prior to the due date of the first installment of such consolidated contract.

(2) When such subsequent purchases are made, if the seller has retained title or taken a lien or other security interest in any of the goods purchased under any one of the contracts included in the consolidation:

(a) The entire amount of all payments made prior to such subsequent purchases shall be deemed to have been applied on the previous purchases;

(b) The amount of any down payment on the subsequent purchase shall be allocated in its entirety to such subsequent purchase;

(c) Each payment received after the subsequent purchase shall be deemed to be allocated to all of the various time balances in the same proportion or ratio as the original cash sale prices of the various retail installment transactions bear to one another: PROVIDED, That the seller may elect, where the amount of each installment payment is increased in connection with the subsequent purchase, to allocate only the increased amount to the time balance of the subsequent retail installment transaction, and to allocate the amount of each installment payment prior to the increase to the time balance(s) existing at the time of the subsequent purchase.

The provisions of this subsection shall not apply to cases where such previous and subsequent purchases involve equipment, parts, or other goods attached or affixed to goods previously purchased and not fully paid, or to services in connection therewith rendered by the seller at the buyer's request.