CAL. BPC. CODE § 6148 : California Code - Section 6148

(a) In any case not coming within Section 6147 in which it is reasonably foreseeable that total expense to a client, including attorney fees, will exceed one thousand dollars ($1,000), the contract for services in the case shall be in writing. At the time the contract is entered into, the attorney shall provide a duplicate copy of the contract signed by both the attorney and the client, or the client's guardian or representative, to the client or to the client's guardian or representative. The written contract shall contain all of the following:

(1) Any basis of compensation including, but not limited to, hourly rates, statutory fees or flat fees, and other standard rates, fees, and charges applicable to the case.

(2) The general nature of the legal services to be provided to the client.

(3) The respective responsibilities of the attorney and the client as to the performance of the contract.

(b) All bills rendered by an attorney to a client shall clearly state the basis thereof. Bills for the fee portion of the bill shall include the amount, rate, basis for calculation, or other method of determination of the attorney's fees and costs. Bills for the cost and expense portion of the bill shall clearly identify the costs and expenses incurred and the amount of the costs and expenses. Upon request by the client, the attorney shall provide a bill to the client no later than 10 days following the request unless the attorney has provided a bill to the client within 31 days prior to the request, in which case the attorney may provide a bill to the client no later than 31 days following the date the most recent bill was provided. The client is entitled to make similar requests at intervals of no less than 30 days following the initial request. In providing responses to client requests for billing information, the attorney may use billing data that is currently effective on the date of the request, or, if any fees or costs to that date cannot be accurately determined, they shall be described and estimated.

(c) Failure to comply with any provision of this section renders the agreement voidable at the option of the client, and the attorney shall, upon the agreement being voided, be entitled to collect a reasonable fee.

(d) This section shall not apply to any of the following:

(1) Services rendered in an emergency to avoid foreseeable prejudice to the rights or interests of the client or where a writing is otherwise impractical.

(2) An arrangement as to the fee implied by the fact that the attorney's services are of the same general kind as previously rendered to and paid for by the client.

(3) If the client knowingly states in writing, after full disclosure of this section, that a writing concerning fees is not required.

(4) If the client is a corporation.

(e) This section applies prospectively only to fee agreements following its operative date.

(f) This section shall become operative on January 1, 2000.