The appellant in this child support case is the mother and the custodial parent of the parties’ three children. She and the appellee were divorced on January 16, 1989, pursuant to a divorce decree which granted the divorce to the appellant, gave her custody of the three minor children, provided visitation privileges for the appellee, and required that the appellee pay child support in the amount of $440.00 per week. On February 2,1990, the appellee filed a petition for modification of the decree, requesting, among other things, modification of child support. The appellant filed a counterclaim, petitioning for modification of the decree and seeking to collect past due child support. On March 26, 1990, a hearing was held and the chancellor entered an order finding that neither of the parties had complied with the divorce decree and that both parties were estopped from raising the issue of back support. Additionally, he *252modified the child support required to be paid by the appellee from $440.00 per week to $62.00 per week. From that decision, comes this appeal.
The appellant advances two arguments on appeal: first, that the trial court erred in finding that she was estopped to raise the issue of the appellee’s failure to pay child support and that there was no child support due on the ground of estoppel and; second, that the trial court erred in modifying the amount of child support in the absence of a showing of changed circumstances. We disagree with the appellant’s arguments and affirm.
Although we review chancery cases de novo, we do not disturb the chancellor’s findings unless they are clearly against the preponderance of the evidence. Ark. R. Civ. P. 52(a). Because the question of the preponderance of the evidence turns largely on the credibility of the witnesses, we defer to the chancellor’s superior opportunity to assess credibility. Callaway v. Callaway, 8 Ark. App. 129, 648 S.W.2d 520 (1983).
The appellant argues that the trial court erred in finding that she was estopped to raise the issue of the appellee’s failure to pay child support. Once a child support payment falls due, it becomes vested and a debt due the payee. Holley v. Holley, 264 Ark. 35, 568 S.W.2d 487 (1987). Arkansas has enacted statutes in order to comply with federal regulations and to insure that the State will be eligible for federal funding. Sullivan v. Eden, 304 Ark. 133, 801 S.W.2d 32 (1990); see Ark. Code Ann. §§ 9-12-314 and 9-14-234 (Repl. 1991). These statutes provide that any decree, judgment, or order which contains a provision for payment of child support shall be a final judgment as to any installment or payment of money which has accrued. Ark. Code Ann. § 9-14-234(a) (Repl. 1991); Ark. Code Ann. § 9-12-314(b) (Repl. 1991); see Sullivan v. Eden, supra. Furthermore the court may not set aside, alter, or modify any decree, judgment or order which has accrued unpaid support prior to the filing of the motion. Ark. Code Ann. § 9-14-234(b) (Repl. 1991); Ark. Code Ann. § 9-12-314(c) (Repl. 1991); See Sullivan, supra. While it appears that there is no exception to the prohibition against the remittance of unpaid child support, the commentary to the federal regulations which mandated our resulting State statutes, makes it clear that there are circumstances under which a court might *253decline to permit the enforcement of the child support judgment. The commentary states:
[enforcement of child support judgments should be treated the same as enforcement of other judgments in the State, and a child support judgment would also be subject to the equitable defenses that apply to all other judgments. Thus, if the obligor presents to the court or administrative authority a basis for laches or an equitable estoppel defense, there may be circumstances under which the court or administrative authority will decline to permit enforcement of the child support judgment.
54 Fed. Reg. 15,761 (April 19, 1989).
In the case before us the chancellor declined to permit the enforcement of the child support judgment claimed by the appellant on the ground that the appellant was estopped because she had disregarded the divorce decree and had interfered with the appellee’s visitation rights. The chancellor determined that both parties ignored the initial divorce decree and were thereby estopped from raising the other’s non-compliance in order to receive any relief. The chancellor based his ruling on the principle that both parties, by their own conduct, had barred themselves from the aid of equity. See Pence v. Pence, 223 Ark. 782, 268 S.W.2d 609 (1954). We think that the chancellor’s action was grounded in the maxim that he who comes into equity must come with clean hands.
This maxim is not applied to favor a defendant, and has nothing to do with the rights or liabilities of the parties, but is invoked in the interest of the public on grounds of public policy and for the protection of the integrity of the court. 30 C.J.S. Equity § 93 (1965); see gen. Estate of Houston v. Houston, 31 Ark. App. 218, 792 S.W.2d 342 (1990). Whether the parties are within the application of the maxim is primarily a question of fact and there must be some evidence to justify the application of the doctrine by the court. 30 C.J.S. Equity § 93 (1965).
The chancellor, in determining from the evidence that the court should refuse to recognize the past due child support, based his decision on the appellant’s testimony referring to the children as “my babies,” her silence when asked to concede the *254fact that they were also the appellee’s children, and her response that she felt that the children are hers and that the appellee is the reason the children see a counselor. The chancellor also considered letters from the appellant to the appellee telling him to leave the children alone, that she did not want him calling the children or coming to see them, that the police would be waiting for him when he returned and would put him in jail, and that she had sold property he left behind and kept the money.
Although there was testimony from the appellant that she did not deny visitation, that she offered to take the children to see him, and that the appellant broke several promises to visit, we cannot say that the chancellor’s determination that the appellant was estopped from asserting and collecting past due child support in a court of equity was clearly against the preponderance of the evidence. On these facts, the chancellor could find unclean hands and properly decline to enforce the judgment. See Marshall v. Marshall, 227 Ark. 582, 300 S.W.2d 933 (1957).
We disagree with the appellant’s argument that the trial court erred in modifying the amount of child support in the absence of a showing of changed circumstance because the record is replete with evidence showing changed circumstances. The party seeking a modification of child support has the burden of showing changed circumstances, and chancery courts have broad powers to modify child support when modification is in the best interest of the child. Guffin v. Guffin, 5 Ark. App. 83, 632 S.W.2d 446 (1982). No hard and fast rule can be established regarding specific changed circumstances or a necessary degree of change. Id. Accordingly, whether a modification in child support is justified by changed circumstances is within the sound discretion of the chancellor, id, and his finding will not be disturbed on appeal in the absence of a showing of an abuse of discretion. Mitchell v. Mitchell, 2 Ark. App. 75, 616 S.W.2d 753 (1981). The record before us shows that subsequent to the divorce the appellee began a different job and he informed the chancellor of his anticipated net income from the new job. The chancellor considered this evidence and applied the Family Support Chart and modified the child support payments accordingly. Furthermore, pursuant to the original divorce decree, the appellee was ordered to pay child support for three children, one of whom was approaching majority and was engaged to be married or was *255married at the time of the modification hearing. Moreover, the appellant admitted that the appellee was unable to make the $440.00 per week child support installments awarded under the original decree when she stated that “[t]here aren’t very many people who can afford $440.00 a week child support, not even him.” She had also sent, in September, 1989, a letter to the appellee agreeing to accept $100.00 per week for child support. Under these circumstances, we hold that the chancellor did not abuse his discretion by applying the Family Support Chart to the appellee’s present net income in order to modify child support from $440.00 per week to $62.00 per week.
Affirmed.
Jennings and Rogers, JJ., dissent.