Cal. Rev. & Tax. Code § 18530

Where the amount shown as the tax by the husband and wife on a joint return made under Section 18522 exceeds the aggregate of the amounts shown as the tax upon the separate return of each spouse, each of the following shall apply:

(a) If any part of the excess is attributable to negligence or intentional disregard of rules and regulations (but without intent to defraud) at the time of the making of the separate return, then 20 percent of the total amount of the excess shall be assessed, collected and paid, in lieu of the 20 percent addition to the tax provided in subdivision (a) of Section 19164.

(b) If any part of the excess is attributable to fraud with intent to evade tax at the time of the making of the separate return, then 75 percent of the total amount of the excess shall be assessed, collected and paid, in lieu of the 75 percent addition to the tax provided in subdivision (b) of Section 19164.