California Code, Government Code - GOV § 26920

(a) At least once in each quarter, the county auditor shall perform, or cause to be performed, a review of the treasurer's statement of assets in the county treasury.Each county shall fund and allocate the cost of the review in accordance with that county's established budgetary practice. The auditor's review shall be accomplished in accordance with the appropriate professional standards, as determined by the county auditor. The treasurer shall prepare a statement showing the amount and type of assets in the county treasury as of the date of the review. The review shall include:

(b) The auditor shall, at least annually, perform or cause to be performed an audit of the assets in the county treasury and express an opinion whether the treasurer's statement of assets is presented fairly and in accordance with generally accepted accounting principles. The audit report shall be addressed to the board of supervisors. The review required by subdivision (a) need not be performed for the period when an audit is conducted in accordance with this subdivision.