dissenting.
I would hold that the trial court abused its discretion in holding that father was entitled to credit for non-conforming child support payments. Therefore, I would reverse the decision of the trial court on all issues, and I respectfully dissent from the majority’s four-part analysis.
Under settled principles,
[cjhild support payments required under a valid court order become vested as they accrue, and the court is without authority to make any change as to past due installments. Generally, the terms of a support decree must be strictly complied with and payments made when due to the designated payee in accordance with the terms of the decree. When changed circumstances dictate a modification of a support decree, the appropriate remedy is for the party to petition the court to modify the decree. The party or parties may not unilaterally or bilaterally vary its terms.
However, although a court may not retroactively modify a child support obligation, allowing a payor spouse credit for non-conforming support payments, in the limited situations where permitted, is not a modification of a support order. See Acree v. Acree, 2 Va.App. 151, 152, 342 S.E.2d 68, 69 (1986). A court may, when equitable and under limited circumstances, allow a party credit for non-conforming support payments, provided that the non-conforming support *726payment substantially satisfies the purpose and function of the support award, see [id.], and to do so does not vary the support award.
Commonwealth v. Skeens, 18 Va.App. 154, 158, 442 S.E.2d 432, 434-35 (1994) (citations omitted) (emphasis added). “Typically, two conditions must exist before credits will be given for non-conforming payments: (1) an agreement by the parties which modifies the terms or method of payment; and (2) no adverse [ejffect on the support award.” Wilderman v. Wilderman, 25 Va.App. 500, 506, 489 S.E.2d 701, 705 (1997). “An agreement which itself establishes or modifies the support obligation, rather than only the terms or method of payment, does not meet this test. Such agreements are not enforceable absent court approval, because they impinge on the child’s right to support and the court’s continuing jurisdiction to decree it.” Id. at 506 n. 1, 489 S.E.2d at 705 n. 1.
We approved one exception to this rule in Aeree, which we recognized involved “unique facts.” 2 Va.App. at 152, 342 S.E.2d at 68. Acree involved a bilateral modification agreement which provided for one of the parties’ children, originally in the custody of her mother, to reside permanently with her father. See id. at 152-53, 342 S.E.2d at 69. In conjunction with this total change in custody, the parties agreed to a cessation of father’s support payments to mother on behalf of that child. See id. at 153, 342 S.E.2d at 69. We held that where a
custodial parent has by his or her own volition entered into an agreement to relinquish custody on a permanent basis and has further agreed to the elimination of support payments and such agreement has been fully performed, ... the purpose to be served by application of an inflexible rule denying credit for non-conforming payments is outweighed by the equities involved.... By assuming [complete] physical custody and total responsibility for the support of the child, the husband fulfilled his obligation under the decree.
Id. at 157-58, 342 S.E.2d at 71-72 (emphasis omitted).
The majority contends that Aeree “exception” is not limited to instances in which the parties have agreed to a total *727transfer of custody. I disagree for two reasons. First, Aeree in fact involved a total transfer of custody and concomitant cessation of child support payments. To the extent that Aeree purports to apply to partial changes of custody, its holding is dicta.
Second, in quoting in Aeree from the Indiana case of Isler v. Isler, we recognized only “ ‘a narrow exception’ ” to the rule prohibiting credit for non-conforming support payments — to be applied in cases involving the total “relinquish[ment of] custody on a permanent basis.” Acree, 2 Va.App. at 157, 842 S.E.2d at 71 (quoting Isler v. Isler, 425 N.E.2d 667, 670 (Ind.Ct.App.1981)) (emphasis omitted from second quotation). To permit modification of a decree by the parties in a case in which the change in custody is less than complete will invite “continuous trouble and turmoil,” the exact difficulties the rule prohibiting credit for non-conforming payments is designed to avoid. Henderlite v. Henderlite, 3 Va.App. 539, 542, 351 S.E.2d 913, 914 (1987).
As the majority recognizes, our holding in Aeree was premised in part on the fact that when a complete change in custody occurs, the parent originally obligated to pay support for that child “ ‘has ... furnished support in a different manner under different circumstances easily susceptible of proof’ ” Acree, 2 Va.App. at 157, 342 S.E.2d at 71 (quoting Isler, 425 N.E.2d at 670) (emphasis added). Where the change in custody is less than total, as occurred in this case, determining whether the agreed-upon reduction in support payments properly corresponds to the greater burden assumed as a result of the increased custodial time is not so “easily susceptible of proof.” Under these circumstances, the agreement does more than alter the terms or method of payment; I would hold, as a matter of law, that it impermissibly modifies the underlying obligation such that a court need not reach the issue of whether it has an adverse effect on the support award. Therefore, I adhere to the long-standing rule that, absent a complete change in custody, “the appropriate remedy” in a case in which the parties have agreed to a modification of support “is for the parties] [timely] to petition *728the court to modify the decree.” Skeens, 18 Va.App. at 158, 442 S.E.2d at 435.
In sum, I would limit Aeree to its facts and hold that the trial court abused its discretion in concluding father was entitled to a credit for non-conforming child support payments under the facts of this case. In addition, under my analysis, father’s exhibit of comparative household expenditures was not relevant to the case and was improperly admitted. Finally, because I would hold that wife should have prevailed in the trial court, I would hold she was entitled to payment of her attorney’s fees pursuant to the parties’ 1991 property settlement agreement. Therefore, I would reverse the decision of the trial court on these issues, and I respectfully dissent from the majority’s four-part analysis.