Child support usually must be paid by the noncustodial parent when the child is with the noncustodial parent for summer vacations or long holiday breaks. Courts reason that many major expenses for the benefit of the child–such as rent, mortgage, utilities, clothes, and insurance–have to be paid whether the child is with the custodial parent or not. So, usually, a full support payment is due, even if the child is with the noncustodial parent.
On the other hand, the parties themselves (or the court) are free to set payments in different amounts during vacation periods when the child is with the noncustodial parent. The lower amount for vacation periods with the noncustodial parent might reflect savings to the custodial parent for food expenses or child care.
A related issue may arise if the noncustodial parent wants to reduce child support payments to the custodial parent because the noncustodial parent has spent money on the child, such as for clothes or extra-curricular activities. That almost never is a basis for reducing child support payments to the custodial parent.
Court orders or divorce settlements almost always provide that child support is to be paid in specific dollar amounts from one parent to the other. Courts do not want the complications of trying to sort out whether the parties on a particular occasion agreed to an alternate way of making child support payments. Courts also do not want the noncustodial parent unilaterally changing the method of paying child support and potentially interfering with the budget planning of the custodial parent.
If the noncustodial parent wants to pay for clothes or extra-curricular activities of the child, that is fine (and nice for the child), but the court will treat such payments as gifts to the child, not as part of the noncustodial parent’s support obligation.