California Code, Probate Code - PROB § 11423

(a) Interest accrues on a debt from the date the court orders payment of the debt until the date the debt is paid. Interest accrues at the legal rate on judgments.

(b) Notwithstanding subdivision (a), in the case of a debt based on a written contract, interest accrues at the rate and in accordance with the terms of the contract. The personal representative may, by order of the court, pay all or part of the interest accumulated and unpaid at any time when there are sufficient funds, whether the debt is then due or not.

(c) Notwithstanding subdivision (a), in the case of a debt for unpaid taxes or any other debt for which interest is expressly provided by statute, interest accrues at the rate and in accordance with the terms of the statute.