Cal. Civ. Code § 1788.52

(a) A debt buyer shall not make any written statement to a debtor in an attempt to collect a consumer debt unless the debt buyer possesses the following information:
1. (1) That the debt buyer is the sole owner of the debt at issue or has authority to assert the rights of all owners of the debt.
2. (2) The debt balance at charge off and an explanation of the amount, nature, and reason for all post-charge-off interest and fees, if any, imposed by the charge-off creditor or any subsequent purchasers of the debt. This paragraph shall not be deemed to require a specific itemization, but the explanation shall identify separately the charge-off balance, the total of any post-charge-off interest, and the total of any post-charge-off fees.
3. (3) The date of default or the date of the last payment.
4. (4) The name and an address of the charge-off creditor at the time of charge off, and the charge-off creditor’s account number associated with the debt. The charge-off creditor’s name and address shall be in sufficient form so as to reasonably identify the charge-off creditor.
5. (5) The name and last known address of the debtor as they appeared in the charge-off creditor’s records prior to the sale of the debt. If the debt was sold prior to January 1, 2014, the name and last known address of the debtor as they appeared in the debt owner’s records on December 31, 2013, shall be sufficient.
6. (6) The names and addresses of all persons or entities that purchased the debt after charge off, including the debt buyer making the written statement. The names and addresses shall be in sufficient form so as to reasonably identify each such purchaser.
7. (7) The California license number of the debt buyer.
(b) A debt buyer shall not make any written statement to a debtor in an attempt to collect a consumer debt unless the debt buyer has access to a copy of a contract or other document evidencing the debtor’s agreement to the debt. If the claim is based on debt for which no signed contract or agreement exists, the debt buyer shall have access to a copy of a document provided to the debtor while the account was active, demonstrating that the debt was incurred by the debtor. For a revolving credit account, the most recent monthly statement recording a purchase transaction, last payment, or balance transfer shall be deemed sufficient to satisfy this requirement.
(c) A debt buyer shall provide the information or documents identified in subdivisions (a) and (b) to the debtor without charge within 15 calendar days of receipt of a debtor’s written request for information regarding the debt or proof of the debt. If the debt buyer cannot provide the information or documents within 15 calendar days, the debt buyer shall cease all collection of the debt until the debt buyer provides the debtor the information or documents described in subdivisions (a) and (b). Except as provided otherwise in this title, the request by the debtor shall be consistent with the validation requirements contained in Section 1692g of Title 15 of the United States Code. A debt buyer shall provide all debtors with whom it has contact an active postal address to which these requests can be sent. A debt buyer may also provide an active email address to which these requests can be sent and through which information and documents can be delivered, if the parties agree.
(d)
1. (1) A debt buyer shall include with its first written communication with the debtor in no smaller than 12-point type, a separate prominent notice that provides:
  “You may request records showing the following: (1) that [insert name of debt buyer] has the right to seek collection of the debt; (2) the debt balance, including an explanation of any interest charges and additional fees; (3) the date of default or the date of the last payment; (4) the name of the charge-off creditor and the account number associated with the debt; (5) the name and last known address of the debtor as it appeared in the charge-off creditor’s or debt buyer’s records prior to the sale of the debt, as appropriate; and (6) the names of all persons or entities that have purchased the debt. You may also request from us a copy of the contract or other document evidencing your agreement to the debt.
  “A request for these records may be addressed to: [insert debt buyer’s active mailing address and email address, if applicable].”
2. (2) When collecting on a time-barred debt where the debt is not past the date for obsolescence provided for in Section 605(a) of the federal Fair Credit Reporting Act (15 U.S.C. Sec. 1681c):
  “The law limits how long you can be sued on a debt. Because of the age of your debt, we will not sue you for it. If you do not pay the debt, [insert name of debt buyer] may [continue to] report it to the credit reporting agencies as unpaid for as long as the law permits this reporting.”
3. (3) When collecting on a time-barred debt where the debt is past the date for obsolescence provided for in Section 605(a) of the federal Fair Credit Reporting Act (15 U.S.C. Sec. 1681c):
  “The law limits how long you can be sued on a debt. Because of the age of your debt, we will not sue you for it, and we will not report it to any credit reporting agency.”
(e) If a language other than English is principally used by the debt buyer in the initial oral contact with the debtor, the notice required by subdivision (d) shall be provided to the debtor in that language within five working days.
(f) A debt buyer shall not collect, or make any attempt to collect consumer debt that originated with a hospital licensed pursuant to subdivision (a) of Section 1250 of the Health and Safety Code without including in the first written communication to the debtor a copy of the notice required pursuant to subdivision (e) of Section 127425 of the Health and Safety Code.
(g) In the event of a conflict between the requirements of subdivision (d) and federal law, so that it is impracticable to comply with both, the requirements of federal law shall prevail.