A contract for the services of an attorney, surveyor, auctioneer, or other third person may provide for the accrual of interest at a rate not in excess of the legal rate for amounts due under the contract that are not paid within three months after the time they become due and payable.
Section 873.150
Code Civ. Proc. § 873.150 — under California Code Civ. Proc..
Code Civ. Proc. § 873.150