69 Pa. Stat. § 1309
If a retail installment sale is sale of goods or services for a cash sale price of fifty dollars ($50) or less, then the retail installment contract need not be contained in a single document. If the contract is contained in more than one document, one such document shall be an original document signed by the retail buyer, stated to be applicable to purchases of goods or services to be made by the retail buyer from time to time. In such case such document, together with the sales slip, account book or other written statement relating to each purchase, shall set forth all of the information required by section 303 and shall constitute a separate retail installment contract for each purchase. On each succeeding purchase pursuant to such original document, the sales slip, account book or other written statement may at the option of the seller constitute the memorandum required by section 803.
69 P.S. § 1309