Cal. Rev. & Tax. Code § 7655.5
(a) If the department finds, taking into account all facts and circumstances, that it is inequitable to compute interest at the modified adjusted rate per month or fraction thereof, as defined in subdivision (b) of Section 6591.5, interest shall be computed at the modified adjusted daily rate from the date on which the tax or prepayment was due until the date of payment, if all of the following occur: