Cal. CCP § 337a

(a) The term “book account” means a detailed statement which constitutes the principal record of one or more transactions between a debtor and a creditor arising out of a contract or some fiduciary relation, and shows the debits and credits in connection therewith, and against whom and in favor of whom entries are made, is entered in the regular course of business as conducted by such creditor or fiduciary, and is kept in a reasonably permanent form and manner and is (1) in a bound book, or (2) on a sheet or sheets fastened in a book or to backing but detachable therefrom, or (3) on a card or cards of a permanent character, or is kept in any other reasonably permanent form and manner. A “book account” does not include consumer debt.

(b) For purposes of this section, “consumer debt” means any obligation or alleged obligation, incurred on or after July 1, 2024, of a consumer to pay money arising out of a transaction in which the money, property, insurance, or services that are the subject of the transaction are primarily for personal, family, or household purposes and where the obligation to pay appears on the face of a note or in a written contract.