Cal. Rev. & Tax. Code § 5153

Notwithstanding Sections 5150 and 5151, whenever the auditor has impounded revenues pursuant to subdivision (a) of Section 26906.1 of the Government Code and those revenues are ultimately used to provide a refund of tax to the affected taxpayer or taxpayers, interest due to the taxpayer or taxpayers for the period that those funds were impounded shall be calculated and paid at the rate, or rates where the applicable rate fluctuated, earned by the county on those revenues during the period of impoundment.