California Code, Civil Code - CIV § 1788.54

(a) All settlement agreements between a debt buyer and a debtor shall be documented in open court or otherwise reduced to writing.  The debt buyer shall ensure that a copy of the written agreement is provided to the debtor.

(b) A debt buyer that receives payment on a debt shall provide, within 30 calendar days, a receipt or monthly statement, to the debtor.  The receipt or statement shall clearly and conspicuously show the amount and date paid, the name of the entity paid, the current account number, the name of the charge-off creditor, the account number issued by the charge-off creditor, and the remaining balance owing, if any.  The receipt or statement may be provided electronically if the parties agree.

(c) A debt buyer that accepts a payment as payment in full, or as a full and final compromise of the debt, shall provide, within 30 calendar days, a final statement that complies with subdivision (b).  A debt buyer shall not sell an interest in a resolved debt, or any personal or financial information related to the resolved debt.