The amount of the determination, exclusive of penalties, shall bear interest at the modified adjusted rate per month, or fraction thereof, established pursuant to Section 6591.5, from the date the amount, or any portion thereof, should have been reported until the date of payment.

(Amended by Stats. 1984, Ch. 1020, Sec. 34. Operative July 1, 1985, by Sec. 65 of Ch. 1020.)