Opinion
ARABIAN, J.In Moffat v. Moffat (1980) 27 Cal.3d 645 [165 Cal.Rptr. 877, 612 P.2d 967], we held that a parent under a court order to pay support for a minor child must pay that support even if the parent with custody interferes with the paying parent’s right to visit with the child. We are now asked to decide whether a custodial parent who not merely interferes with visitation rights, but actively conceals the parent and child from the other parent until the child becomes an adult may thereafter seek arrearages for child support obligations accrued during the period of concealment. The Courts of Appeal are divided on the question to what extent, if any, concealment is a defense to the obligation to pay child support.
Concealment of the child and the custodial parent from the noncustodial parent until the child reaches the age of majority is different from mere *676interference with visitation both in degree and in kind. As a difference in degree, it obliterates the entire relationship between the child and the noncustodial parent. This alone may not be sufficient to warrant a different rule than that of Moffat v. Moffat, supra, 27 Cal.3d 645. As a difference in kind, however, it makes impossible performance of the very child support payments that are the subject of the later arrearages action. This does distinguish Moffat. We conclude that such concealment may estop the custodial parent from seeking payment of child support arrearages which accumulated during the period of concealment. We therefore affirm the judgment of the Court of Appeal, which reached the same result.
Facts
Appellant Ronald Damico (father) and respondent Mary Damico Austin (mother) were married in 1958 and separated less than a year later. A son was born to them on September 22, 1958. A judgment of divorce was entered in May 1960 which ordered father to pay child support. He paid the support for a short time, then stopped under circumstances that are disputed. In 1979, father was served with an application for child support arrearages. A default judgment was entered against him in June 1980 in San Francisco Superior Court determining that he owed $12,948.50 in child support arrearages from May 1959 through September 1978, plus interest in the amount of $10,264.22.
In January 1991, the Marin County District Attorney, acting on behalf of mother, filed a statement for registration of foreign support order, and served father. Father moved to vacate the registration of the foreign support order and the prior default judgment. At a hearing in August 1991 to determine the amount of arrearages, if any, father owed, he offered to prove the following.
In 1960, he visited with mother and the child in San Francisco. Mother told father that “she did not want [him] to see the child ever again and that [he] would not see the child ever again. She wanted [him] to remove [himself] from her life and from the child’s life.” Mother’s brother then assaulted him with a knife, forcing him to flee. Father tried to call her several times to arrange to visit with the child, but the person answering would hang up as soon as he identified himself. Soon thereafter, mother “dropped out of sight and [father] could not find her or the child” despite numerous attempts to locate and contact them. From 1960 until 1979, after the child had become an adult, father “had no way of contacting or paying support to them.” No one contacted him seeking support even though he was readily available. Father “had given up all hope of ever contacting [his] son in that [he] thought that [mother] had made good on her promise of never *677letting [him] see the child, and had effectively secreted the child from [him].”
In 1979, according to the offer of proof, father was “shocked and amazed” to be served with the application for child support arrearages. He hired counsel to represent him in that proceeding, and he “moved to Arizona believing that this matter had been taken care of by that attorney.” He later learned that his attorney did not appear for him, and a default judgment was entered. Father claims that had he “had knowledge of the whereabouts of [his] child and the [mother], [he] would have made payments in a timely fashion and attempted to visit [his] child in a responsible manner.”
Mother filed a declaration in which she denied concealing the child from father. Rather, she claimed, father threatened to “abduct” the child, and did not pay child support. In 1963, after she remarried, she had the child’s last name legally changed to her husband’s surname. From 1964 until 1978, she “had no contact with [father], nor did [she] have any knowledge about how to locate him." Finally, in 1978, she was able to locate father and serve him with a motion for an order fixing arrearages.
The trial court ruled that father’s offer of proof was not relevant to the issue of arrearages, and refused to consider his “concealment” defense. No evidentiary hearing on the question was held. The court ultimately ordered father to pay the entire amount of arrearages plus interest. Father appealed.
The Court of Appeal reversed. It rejected mother’s argument that the earlier default judgment precluded father from raising the concealment defense at this time. It then held that while mere interference with visitation rights by the custodial parent does not present a defense to the enforcement of a child support order, active concealment does. It remanded the case for the parties to present evidence on the question of concealment.
Mother petitioned this court to review whether “evidence of a custodial parent’s concealment of a child who is the subject of a child support order [is] admissible to estop the custodial parent from claiming child support arrearages from the absent parent for the period of concealment.” We granted the petition.1
*678Discussion
In Moffat v. Moffat, supra, 27 Cal.3d 645 (Moffat), we construed Code of Civil Procedure former section 1694, part of the Revised Uniform Reciprocal Enforcement of Support Act, which provided in pertinent part: “The determination or enforcement of a duty of support owed to one obligee is unaffected by any interference by another obligee with rights of custody or visitation granted by a court.”
Also pertinent to this question is Civil Code former section 4382, which provided: “The existence or enforcement of a duty of support owed by a noncustodial parent for the support of a minor child shall not be affected by a failure or refusal by the custodial parent to implement any rights as to custody or visitation granted by a court to the noncustodial parent.” This latter section was part of the chapter providing for the enforcement of judgments, orders and decrees under the Family Law Act. It was enacted before, but took effect after, the decision in Moffat, supra, 27 Cal.3d 645. (Stats. 1980, ch. 237, § 1, p. 480; see In re Marriage of Smith (1989) 209 Cal.App.3d 196, 201 [257 Cal.Rptr. 47].) It is not discussed in Moffat.2
The cases construing these statutes assume that, although each uses slightly different language, the meaning of both is substantially identical, at least as regards the issue in this case. The parties do not suggest the statutes have different meanings. We doubt that the Legislature intended different rules to apply to proceedings under RURESA (now URESA) and the Family Law Act. The statutory language does not compel such a conclusion. We therefore construe the statutes as identical for purposes of this issue.
In Moffat, supra, 27 Cal.3d 645, the custodial mother had “obdurately refused to comply with the visitation order and ha[d] thus denied the children their right to know and to be with their father.” (Id. at p. 650.) Because of the mandate of Code of Civil Procedure former section 1694, we held that this circumstance did not provide a defense to the obligation to pay child support. We emphasized we did not approve of the custodial parent’s conduct, but concluded that “in such circumstances the child’s need for sustenance must be the paramount consideration.” (27 Cal.3d at p. 651.)
*679We noted, however, that although “RURESA provides no forum for litigating disputes over interference with custody and visitation rights, a noncustodial parent in the position of Mr. Moffat is not bereft of remedy. Such rights are initially determined by the superior court, acting under authority of the Family Law Act. (Civ. Code, § 4351.) Thus the parent whose rights are in jeopardy may seek enforcement of the judgment, order, or decree in the rendering court. (Id., § 4380.)” (Moffat, supra, 27 Cal.3d at pp. 651-652.) We listed “several appropriate sanctions when the custodial parent acts with an intent to frustrate or destroy visitation rights,” including contempt proceedings, terminating or reducing spousal support, modifying custody or child support orders, and requiring a bond to assure compliance with the visitation order. (Id. at p. 652.) But as regards the noncustodial parent’s obligation to continue to pay child support, we concluded that “by her misconduct alone in depriving the father of his visitation rights, [the custodial parent] is not estopped from pursuing the enforcement of child support under RURESA.” (Ibid.; see also id. at p. 659 [“section 1694 bars the assertion of interference with visitation rights as a defense in a RURESA proceeding in which the duty of support is being determined”].)
Father does not challenge the holding of Moffat, but argues that it does not apply when the custodial parent engages in active concealment. The Court of Appeal here agreed: “A distinction has been recognized, however, between mere interference with visitation rights by the custodial parent, which the controlling statutes expressly foreclose as a defense to enforcement of a child support order, and active concealment of the child, which falls outside the purview of sections 1694 and 4382. (In re Marriage of Smith (1989) 209 Cal.App.3d 196, 201-202 [257 Cal.Rptr. 47]; State of Washington ex rel. Burton v. Leyser (1987) 196 Cal.App.3d 451, 457 [241 Cal.Rptr. 812] (hereafter Leyser); In re Marriage of Kelley [1986] 186 Cal.App.3d 613, 618-619 [231 Cal.Rptr. 6]; Solberg v. Wenker (1985) 163 Cal.App.3d 475, 478 [209 Cal.Rptr. 545]; In re Marriage of Daves (1982) 136 Cal.App.3d 7, 10 [185 Cal.Rptr. 770].) We are persuaded that the distinction is a valid one, based upon the statutory language and rationale underlying the legislation.
“Sections 1694 and 4382 specifically provide that the child support obligation is not extinguished by the custodial parent’s ‘interference’ with or ‘refusal ... to implement’ visitation granted by the court, conduct which we do not equate with deliberate ‘sabotage’ of visitation rights by concealment of the child. (In re Marriage of Smith, supra, 209 Cal.App.3d at p. 201; Solberg v. Wenker, supra, 163 Cal.App.3d at p. 458.) Thus, we find nothing in the language of the statutes which expressly prohibits an estoppel defense to an action for collection of child support arrearages based upon active concealment of the child. Had the Legislature intended to grant an exemption from equitable defenses to conduct which so subverts the parent-child *680relationship, we believe the terms ‘interference’ with and ‘refusal ... to implement’ visitation rights would have been replaced with much more encompassing language.
“We are also convinced that the primary objective of the statutes—that is, the child’s sustenance and welfare—cannot be served where the custodial parent seeks an award of arrearages after the child has been concealed until reaching the age of majority. [Fn. omitted.] (In re Marriage of Smith, supra, 209 Cal.App.3d at pp. 202-203; Leyser, supra, 196 Cal.App.3d at p. 458.) In such a case, reimbursement to the custodial parent will not cognizably advance the child’s welfare. (Ibid.) We see no reason to reward a custodial parent who has concealed the whereabouts of a child, and thereby denied the values inherent in a congenial parent-child relationship, with a belated award of support arrearages which will be of no tangible benefit to the child. (Moffat, supra, 27 Cal.3d at p. 658.) The welfare of a child ‘transcends material considerations. . . . Visitation rights are a two-way street: although technically awarded by a court to a parent, the rights belong equally to the children. Thus the Legislature and our courts alike have declared an abiding parental relationship to be in the best interests of the child. [Citations.]’ (Ibid.; see also In re Marriage of Smith, supra, 209 Cal.App.3d at pp. 202-203; Leyser, supra, 196 Cal.App.3d at p. 457.) Without a clear and convincing directive from the Legislature, we decline to permit a custodial parent to undermine the parent-child relationship by active concealment of the child—which we view as an implicit election to raise the child without financial assistance from the noncustodial parent—with no disruption of the corollary right to reimbursement for child support arrearages. And finally, while a noncustodial parent who has suffered mere interference with visitation rights has several feasible alternative remedies—i.e., an order of contempt, an order terminating or reducing spousal support, an order changing custody, or a bond to assure compliance with visitation orders—the case is otherwise where the custodial spouse has engaged in purposeful concealment. In such circumstances, the noncustodial spouse has no practical means of employing these remedies and may have no recourse other than to claim concealment as a defense to collection of child support arrearages. (Id. at p. 459; Solberg v. Wenker, supra, 163 Cal.App.3d at p. 480.)” (Italics in original.)
In State of Washington ex rel. Burton v. Leyser (1987) 196 Cal.App.3d 451 [241 Cal.Rptr. 812] (Leyser), cited by the Court of Appeal here, the mother concealed her whereabouts and that of the children who were the subject of a child support order for several years, until the 2 children were 12 or 13 and 17 years old, respectively. The trial court refused to order the father to pay arrearages for the period of the concealment. The Court of Appeal affirmed. *681It expressly found it “need not address the issue of whether . . . ‘concealment’ is a distinct defense to an action for child support arrearages under RURESA,” holding instead that both waiver and estoppel were valid defenses. (Id. at p. 455.) The court “agree[d] the principal concern in litigating the right to current and future child support is the welfare of the child. However, when past unpaid support is the issue, the welfare of the child may not be involved. For example, in this case reimbursement to the mother will have no tangible effect on [the older child], whose locátion is unknown. Quite different considerations would be present if a public agency had provided support for the benefit of the children and was seeking reimbursement. A public agency cannot be estopped because of the conduct of the parents. (In re Marriage of Kelley (1986) 186 Cal.App.3d 613, 620-621 [231 Cal.Rptr. 6].) Also, if the ongoing support of the child is at issue, our high court in Moffat and the Legislature by its enactments on the subject, have made it clear the child’s right to sustenance must remain free of the disputes or express or implied agreements of the parents.” (Id. at p. 457, italics in original.)
The Leyser court thus found “a proper distinction between ongoing interference with visitation which is subject to litigation and relief, and past conduct amounting to waiver and/or estoppel of prior support.” (Leyser, supra, 196 Cal.App.3d at p. 458.) “Waiver is the intentional relinquishment of a known right. [Citation.] ... ‘To constitute waiver, it is essential that there be an existing right, benefit, or advantage, a knowledge, actual or constructive, of its existence, and an actual intention to relinquish it or conduct so inconsistent with the intent to enforce the right in question as to induce a reasonable belief that it ha.s been relinquished.’ [Citation.] [ft Estoppel by conduct is very similar and is found when one person intentionally and deliberately leads another to believe that a particular thing is true and to act upon such belief. [Citations.] [ft . . . [I]t was not unreasonable for the trial court to conclude [the mother’s] conduct was inconsistent with her right to reimbursement for sums she expended to support the children during that time. Nor was it unreasonable to conclude she induced [the father] to believe she would not claim child support for that period of time.” (Id. at p. 460; see also In re Marriage of McLucas (1989) 210 Cal.App.3d 83 [258 Cal.Rptr. 133].)
A different view was taken in In re Marriage of King (1993) 16 Cal.App.4th 1250 [20 Cal.Rptr.2d 486]. There, the noncustodial father did not know where the children were for three months one summer while the children were still minors. Expressly disagreeing with the Court of Appeal in this case and Solberg v. Wenker (1985) 163 Cal.App.3d 475 [209 Cal.Rptr. 545], the court held that “a noncustodial parent’s ignorance of the whereabouts of his children is not a defense to the obligaton to pay child support *682arrears even where the ignorance stems from the custodial parent’s concealment of the children.” (In re Marriage of King, supra, 16 Cal.App.4th at p. 1251.) The court reasoned, “First, Civil Code section 4382 is not ambiguous. [Fn. omitted.] The statute directs that enforcement of child support ‘shall not be affected by a failure or refusal ... to implement . . . custody or visitation [rights] . . . .’ There can be no doubt that child concealment is encompassed within the broad concept of a failure or refusal to implement custody or visitation rights. (Civ. Code, § 3536 [‘The greater contains the less.’].) That child concealment could be called deliberate sabotage of visitation rights does not alter this fact. At most, child concealment is an aggravated form rather than a concept outside the definition of failure or reftisal to implement. In short, the Legislature’s statement of the law is clear and unconditional. It does not except aggravated forms of failures or refusals to implement custody or visitation rights from its directive. (In re Marriage of Tibbett [(1990) 218 Cal.App.3d 1249, 1254 (267 Cal.Rptr. 642)].)
“Second, ‘Solberg relies on suspect authority—cases that predate [Civil Code section 4382] as well as cases that do not discuss th[is] relevant authorit[y].’ (In re Marriage of Tibbett, supra, 218 Cal.App.3d at p. 1253.)
“ ‘The Supreme Court has held that tide Legislature intended to separate support and visitation rights—that a custodial parent’s misconduct cannot estop that parent from asserting a child’s support rights. [Citation.] Regardless of whether the custodial parent actually conceals the children from the noncustodial parent or merely interferes with their visitation, these authorities apply with equal force. While we do not condone any custodial parent’s deprivation of the visitation rights of a noncustodial parent, we find that concealment does not constitute a defense to [a proceeding to determine child support arrears.]’ (In re Marriage of Tibbett, supra, 218 Cal.App.3d at p. 1254.)” (In re Marriage of King, supra, 16 Cal.App.4th at pp. 1253-1254; see also In re Marriage of Tibbett (1990) 218 Cal.App.3d 1249 [267 Cal.Rptr. 642] [no defense that mother concealed the children for several years ending when the children were still minors]; and Puig v. Ryberg (1991) 230 Cal.App.3d 141, 144 [283 Cal.Rptr. 604] [dicta indicating agreement with Tibbett].)3
We agree with the result the Court of Appeal reached in this case, although for somewhat different reasons. Concealment of the custodial *683parent and child from the noncustodial parent until the child is an adult interferes in an extreme manner with visitation rights. To the extent it does only that, however, it arguably is but a species of interference within the meaning of Code of Civil Procedure former section 1694 (now Fam. Code, § 4845) and Civil Code former section 4382 (now Fam. Code, § 3556), which interference does not prevent enforcement of the child support order. Therefore, unlike the Court of Appeal, we do not rely on that aspect of concealment in finding estoppel.
But such concealment does much more. It effectively precludes the noncustodial parent from invoking or benefitting from the remedies for interference that we identified in Moffat, supra, 27 Cal.3d at page 652, and precludes the very child support payments that the custodial parent later seeks to collect. One cannot make child support payments to a person who cannot be located. Concealment thus defeats the entire purpose of the order, which is to provide support to a third party, the child. In finding an estoppel defense under these facts, we rely on the unfairness of enforcing a judgment against a person who had no clear way of paying the monthly obligation because the custodial parent had gone into hiding. It is unfair to let the parent hide during the term of the obligation—usually a lengthy term—and then reappear and demand payment of arrearages in full after he or she has defeated the purpose of the judgment. If the Legislature had intended to make child support obligations unaffected by such concealment, i.e., by conduct making impossible the child support payments themselves, it could have and surely would have used more expansive language than it did.
This conclusion is bolstered by the fact the Legislature has recently recognized the possible validity of an estoppel defense to the enforcement of child support orders. Welfare and Institutions Code section 11350.6, enacted in 1992, concerns enforcement of child support obligations. Subdivision (a)(5) of that section defines the term “‘[cjompliance with a judgment or order for support’ ” as including the situation when the obligor “has obtained a judicial finding that equitable estoppel as provided in statute or case law precludes enforcement of the order.” (Italics added.) The Attorney General suggests this merely recognized ‘the vagaries of sister-state judgments which may be based on equitable defenses which are not available in California, but which must be accorded full faith and credit.” Nothing in the statute, however, suggests it is limited to out-of-state judgments.
*684The Attorney General argues on behalf of mother that father, and any noncustodial parent, is not entirely helpless against attempts to conceal a child. A noncustodial parent may, for example, make use of the services of the district attorney and the California Parent Locator Service in an attempt to locate the missing parent. (See Welf. & Inst. Code, § 11478.5; Leyser, supra, 196 Cal.App.3d at p. 459.) Any such attempt may or may not succeed, depending on how successful the custodial parent is in the concealment effort. If it succeeds, then obviously the concealment would end, thus mooting the point at least prospectively, although such success could not remedy the effects of past concealment and the inability to make the support payments during the period of concealment. If it fails, the availability of this assistance would clearly be no remedy at all.
Whether father acted with reasonable diligence in this case, or simply gave up after encountering the first difficulty in finding the child, is a factual question for the trial court to decide. (Leyser, supra, 196 Cal.App.3d at p. 459.) But if mother did in fact conceal herself and the child, thus preventing the payments, she should not now be heard to claim that father did not make herculean efforts to stymie her, and must therefore pay her for all the years she prevented the child from receiving the support. “[Practical difficulties arise when one party is making purposeful efforts to ‘hide.’ ” (Ibid.) “Appellant cannot play hide-and-seek with respondent and then recover support payments for that period of time during which she successfully kept her whereabouts unknown to him.” (Szamocki v. Szamocki (1975) 47 Cal.App.3d 812, 819 [121 Cal.Rptr. 231], quoted in Solberg v. Weaker, supra, 163 Cal.App.3d at p. 480.)
The noncustodial parent who could not find the child and custodial parent could conceivably move in court for a modification of the child support order. Assuming the concealment was successful, such a motion would necessarily be heard without actual notice to the custodial parent. We need not decide whether a trial court would or should modify a support order under such circumstances, for we believe that, although the parent under court order to pay support should always turn to the court for aid when the judgment creditor has made the payments impossible, rather than relying on self-help, we focus on the conduct of the custodial parent in finding estoppel. The custodial parent should not be allowed to make the payments impossible, then seek arreareages after the purpose of the judgment, payment of support for the benefit of the child, has been defeated.
Of course, as noted in Leyser, supra, 196 Cal.App.3d at page 457, when the noncustodial parent does locate the other parent and child, any prior concealment would not affect a continuing obligation to pay child support. *685Here, however, father has no ongoing obligation since the child reached the age of majority before the concealment ended.
The Attorney General also argues that the actions of one parent should not diminish the child’s right to support. We agree in the abstract, but that is not now at issue. Mother’s actions, assuming for the moment the truth of father’s as yet unproven allegations, already have deprived the child of the father’s support. Indeed, the child for whose support mother seeks the arrearages is now 35 years old. Mother is seeking payment of the arrearages to herself, not to the child. The harm mother did to the child by denying it father’s companionship and financial support should not now entitle her to arrearages, many years later, that can no longer benefit the child.
We thus conclude that a custodial parent who actively conceals him- or herself and the child from the noncustodial parent until the child reaches the age of majority, despite reasonably diligent efforts by the noncustodial parent to locate them, is estopped from later collecting child support arrearages for the time of the concealment. Because it is the inability to make the support payments that distinguishes concealment from mere interference, the concealment, to be a defense, must be of both the custodial parent and the child. We disapprove of decisions by the Courts of Appeal to the extent they are inconsistent with this conclusion.
This case involves alleged concealment until the child reached the age of majority. Therefore, we cannot, and do not, express an opinion on the rule when the concealment ends while the child is still a minor and might yet benefit from payment of the arrearages. Because estoppel is an equitable defense, the equities might be different if the concealment were for a shorter time, especially if the innocent child particularly needed the arrearages. This case also does not involve public assistance payments or the assignment of child support rights to a county or other governmental entity, and we therefore do not decide any questions related to those circumstances. (Cf. In re Marriage of Smith, supra, 209 Cal.App.3d 196, with Leyser, supra, 196 Cal.App.3d at p. 457, and In re Marriage of Kelley (1986) 186 Cal.App.3d 613, 619-621 [231 Cal.Rptr. 6].)
We also emphasize, as did the Court of Appeal, that we are ruling only on the relevance, not the credibility, of father’s allegations, which are disputed. The facts will have to be determined by the trial court on remand.
*686Conclusion
The judgment of the Court of Appeal is affirmed.
Lucas, C. J., Mosk, J., George, J., and Boren, J.,* concurred.
In response to Justice Kennard’s concurring opinion, we note that the Court of Appeal rejected mother’s argument that the default judgment precluded raising the concealment defense at this time. In conformity with California Rules of Court, rule 29.2(a), which states that this court “may review and decide any or all issues in the cause,” we granted review of only the issue concerning the viability of the concealment defense, which was, indeed, the only issue raised in the petition for review. The question of the effect of the default judgment *678has not been briefed in this court (see Cal. Rules of Court, rule 29.3(c)) and, given the limited nature of the issue we are reviewing, is not now before us.
In 1992, both Code of Civil Procedure section 1694 and Civil Code section 4382 were repealed and made part of the new Family Code, operative January 1, 1994. (Stats. 1992, ch. 162, §§ 3, 6; see new Fam. Code, §§ 4845, 3556.) The Revised Uniform Reciprocal Enforcement of Support Act (RURESA) has been renamed the Uniform Reciprocal Enforcement of Support Act (URESA) for consistency with the usage of the National Conference of Commissioners on Uniform State Laws. (Fam. Code, § 4800, and the Law Revision Commission Comments thereto.)
We have reviewed out-of-state authority and find it inconclusive. In State ex rel. Southwell v. Chamberland (Minn. 1985) 361 N.W.2d 814, the court refused to recognize a concealment defense. But there the concealment was for a far shorter period of time than here, a governmental entity was seeking the arrearages, and the court did not consider an estoppel argument. Closest on point is State ex rel. Blakeslee v. Horton (1986) 222 Mont. 351 [722 P.2d 1148] where both parties agreed each would stay out of the other’s life despite a court order requiring father to pay child support. Fourteen years later, mother sought the arrearages. In effect adopting an estoppel defense, the court held that the mother should not be allowed *683to participate in the nullification of the law, then later claim the benefit. “Although legally the mother may have been correct in her claim for child support, equity demands that her claim must fail.” (Id. at p. 1151.) Mother’s unilateral actions in this case, if proven, compel a similar result. The other cases cited by Justice Baxter in his dissenting opinion generally only reiterate the California rule stated in Moffat, supra, 27 Cal.3d 645, which we do not question, or are even further removed from the issue here.
Presiding Justice, Court of Appeal, Second Appellate District, Division Two, assigned by the Acting Chairperson of the Judicial Council.