The amount required to satisfy a money judgment is the total amount of the judgment as entered or renewed, plus costs added after judgment and accrued interest on the judgment, minus any payments or partial satisfactions or amounts no longer enforceable [Ca Civ Pro - 695.210]. The principal amount of the judgment is the amount of the judgment as entered or as last renewed, together with any costs added to the judgment, reduced by any payments or partial satisfactions or amount no longer enforceable [Ca Civ Pro - 680.300].
The judgment creditor is entitled to recover interest on the principal amount of the judgment that remains unsatisfied [Ca Civ Pro - 685.010(a)].
Effective January 1, 1983, the rate of interest on a money judgment is 10% per annum. [Ca Civ Pro - 685.010(a)] Interest accrues from the day the judgment is entered. [Ca Civ Pro - 685.020(a)] Where the judgment is payable in installments (e.g., support judgments), interest accrues from the date each installment becomes due unless the judgment provides otherwise. [Ca Civ Pro - 685.020(b)]
Post judgment interest is not compounded (i.e., interest is not paid on the accrued interest) unless the judgment is renewed. When a judgment is renewed, whatever interest has accrued on the original judgment is added to and becomes part of the principal amount of the judgment [See Comment to Ca Civ Pro - 683.110]. Thereafter, interest accrues on the total amount of the renewed judgment (i.e., including the amount added as interest). In effect, the judgment creditor recovers "interest on interest".
If a judgment is partially satisfied by levying a writ or otherwise, interest ceases to accrue as to the part satisfied on the date the part is satisfied. Tender of partial payment to the judgment creditor, or deposit in court, has the same effect as actual payment. [Ca Civ Pro - 685.030(c), (d)]
Partial payments must be applied first to the accrued interest on the judgment. Partial payments reduce the principal judgment only after all accrued interest is paid.
With regard to support orders, interest accrues only on overdue installments under the initial support order, whether it is a temporary or final order and whether or not it is contained in a judgment. An order fixing arrearages under the initial support order or establishing a periodic payment plan to liquidate arrearages under the initial order is not a new installment judgment for support that itself accrues interest. [Ca Fam - 155]
The date interest ceases to accrue on a money judgment satisfied by levying writ of execution depends upon the manner in which the proceeds are collected:
In levying a writ of execution, the levying officer must add interest at the daily interest rate shown on the writ from the date it was issued until interest ceases to accrue (above). In cases of partial satisfaction, the levying officer may, in conformity with his or her office policy, recompute the amount of daily interest accruing on the money judgment. [See Ca Civ Pro - 685.050(b)(2)]
The 10% annual interest rate applies to sister-state judgments from and after the date they are entered as California judgments (Ca Civ Pro - 1710.25(b)). Interest accrued thereon prior to the date of such entry is computed at whatever interest rate is provided under the law of the state where the judgment was rendered. [Ca Civ Pro -- 1710.15, 1710.25]