Where father testified that his wife agreed to the reduction in child support on the condition that he help his son find a place to live and that he support him financially, where father testified further that he paid his son more than $4,000 over a two year period for housing, food and clothing, and where according to father, mother did not at any time during the almost five year period between the first reduced payment and the filing of her petition for arrearages object to the reduction in child support payments, father's payments to his son were made in reliance upon the statements and conduct of mother and, therefore, mother was equitable estoppel.

Child support payments become a vested right as they accrue and cannot be unilaterally terminated by the defendant, and neither can they be modified as to amount or time of payment. In the proper case, however, courts will give effect to an agreement between the parties to waive or reduce payments, or courts will apply the doctrine of equitable estoppel Where the mother, who was the custodial parent under the divorce decree, either consented to or acquiesced in a child living with the father and the father supported the child, the doctrine of equitable estoppel may be applied to allow the father an equitable custody. The test has also been stated more broadly to be whether the conduct of the plaintiff mother, as shown by all the circumstance of the case, was sufficient to justify the conclusion that the enforcement of the decree as to unpaid support would be unjust and inequitable to the defendant father.

In cases allowing an equitable credit against support arrearages, the essential element of detrimental reliance has been present; that is, the court has found that the defendant father relied upon the plaintiff mother's conduct indicating her willingness to give up or modify her right to custody or support.

It is well-established that past-=due installments for child support are the vested rights of the designated recipients and the court lacks the authority to modify those amounts which have already accrued; therefore, any modification in child support payments will only act prospectively.

The required elements for equitable estoppel were not presented where the plaintiff had not by her conduct caused the defendant to suffer any irreparable harm, the failure on the plaintiff's part to make any demand on the defendant until five years after the defendant reduced payment did not create an equitable estoppel, and the record did not reveal that there was an agreement between the parties to reduce the amount due for child support nor did it indicate that the defendant relied upon any conduct by the plaintiff.

Payments

Even though ex-husband was paid bi-monthly, he could be ordered to make weekly payments, and the trial court was within its discretion to order an increase in child support to $90 per week.

Trial court did not err in refusing to abate child support payments for the time during which husband claimed that he did not know the whereabouts of the wife and child and this section precluded any modification of child support payments which had accrued. Trial court did not err in refusing to abate child support payments for the time during which husband claimed that he did not know the whereabouts of the wife and child and this section precluded any modification of child support payments which had accrued.