Casey, J. (concurring in part and dissenting in part). Family Court Act § 413 (1) (b) (1) establishes a formula for calculating the "[b]asic child support obligation” and courts are required by Family Court Act § 413 (1) (f) to order the "non-custodial parent [to pay his or her] pro rata share of the basic child support obligation”, unless that obligation is found to be unjust or inappropriate based upon consideration of certain factors. It is our view that when the parties have joint custody and the actual physical custody of the children is shared to the extent present in this case, the basic child support obligation is, as a matter of law, inappropriate. Accordingly, we respectfully dissent from so much of the majority decision as concludes to the contrary.
The case of Matter of Kerr v Bell (178 AD2d 1) involved a split custody situation, where four children resided with one parent and a fifth resided with the other parent. Recognizing "that it is possible to apply the [basic child support obligation] formula in the split custody context, even if it is unwieldly” (supra, at 3), this Court declined to hold the formula inapplica*189ble. In the Kerr case, each parent was clearly a custodial parent with respect to the child or children who resided with him or her, and at the same time a noncustodial parent with respect to the child or children who resided with the other parent. Here, in contrast, the parties’ two children do not reside with either parent on a full-time basis. Rather, physical custody of both children is shared. During the period that petitioner has physical custody of the children, she is actually the custodial parent and respondent is the noncustodial parent; during the period that respondent has physical custody of the children, he is actually the custodial parent and petitioner is the noncustodial parent. In contrast to the split custody situation in Kerr, the parties herein are never simultaneously both a custodial parent and a noncustodial parent. Rather, their status as the actual custodial parent or noncustodial parent changes back and forth as the physical custody of the children changes. Thus, contrary to the majority’s conclusion, the parents here are not, in effect, simultaneously custodial and noncustodial parents.
Family Court Act § 413 clearly does not contemplate the type of shared custody involved herein, and the practical difficulties inherent in having the obligation to pay child support, imposed by the statute on the noncustodial parent, exchange back and forth between the parties depending upon which of them has physical custody of the children would make application of the statute more than unwieldly. It is our view that, consistent with the intent of the statute, one of the parents in a shared custody arrangement should be viewed as the custodial parent of the parties’ children and the other as the noncustodial parent for the purpose of determining child support under the statute. In this case, petitioner should be viewed as the custodial parent for the purposes of applying Family Court Act § 413 because she has physical custody of the children for the majority of the time. Respondent, therefore, is the noncustodial parent within the meaning of the statute, and the period when he has physical custody of the children constitutes "extended visitation” within the meaning of the statute.
Pursuant to Family Court Act § 413 (1) (f) (9) (ii), the factors which must be considered in determining whether the basic child support obligation created by the statute is "unjust or inappropriate” include "expenses incurred by the non-custodial parent in extended visitation provided that the custodial parent’s expenses are substantially reduced as result thereof’. *190It is our view that this standard has been met as a matter of law when, as in this case, the noncustodial parent’s "extended visitation” consists of actual physical custody of the parties’ children for approximately 40% of the year, as found by the majority. There can be little doubt that a parent who has physical custody of two children for 40% of the year incurs expenses as a result thereof, and that the other parent’s expenses are substantially reduced by not having physical custody of the children for more than 60% of the year. Child support should, therefore, be determined pursuant to Family Court Act § 413 (g).
Mikoll, J. P., and Harvey, J., concur with Crew III, J.; Casey and Mahoney, JJ., concur in part and dissent in part in a separate opinion by Casey, J.
Ordered that the order is reversed, on the law, without costs, and matter remitted to the Family Court of Saratoga County for further proceedings not inconsistent with this Court’s decision.