(concurring specially and concurring in result).
The law and the public policy requiring court approval of child support modifications is sound and deserving of our support. It seems clear, however, that an accord and satisfaction occurred here. Otherwise, Donna would not have had any decision to “regret.” In addition, the offensive letter arrived simultaneously with the check marked “paid in full.” Instead of returning the check, Donna cashed it and then took issue with the letter and the amount claimed owed. I believe the trial court could have approved this agreement between consenting adults because this was all past-due support as all of the children had reached their majority. Neither the law nor public policy should be interpreted so strongly as to promote or approve fraud in inducing payments from a reluctant obligor in future cases. We and the trial court retain the right to review such cases. See Taylor v. Ellenbecker, 471 N.W.2d 587 (S.D.1991); Claudia Catala-no, J.D., Annotation, Spouse’s Right to Set Off Debt Owed by Other Spouse Against Accrued Spousal or Child Support Payments, 11 A.L.R. 5th 259 (1993) and cases cited therein.
I concur in result on Issue 3, prejudgment interest.
SDCL 25-7-7.4 provides:
Unpaid payment or installment of support as judgment. Any payment or installment of support under an order for support, as defined by § 25-7A-l, whether entered by a court or an administrative entity of this state or of any other state or jurisdiction, which is unpaid after the date it is due, is a judgment by operation of law, with the full force, effect and attributes of a judgment of this state, including enforceability, and is entitled, as a judgment, to full faith and credit in this state.
I realize that this court has previously stated that an award of interest on support arrearages is a matter of judicial discretion. See majority opinion (citing Kier, 454 N.W.2d at 546, SDCL 21-1-13.1 and 15-16-3). A plain reading of SDCL 25-7-7.4 as set forth above makes it clear that interest is due on any unpaid installment of support from “the date it is due” by operation of law. Therefore, interest would not be discretionary under SDCL 21-1-13 but mandatory under SDCL 25-7-7.4, 21-1-11, 54-3-5 and 54-3-5.1.