Any annual fee for child support services imposed by the child support agency under section 50-06.3-02 to conform with title IV-D of the Social Security Act [Pub. L. 93-647; 88 Stat. 2351; 42 U.S.C. 651 et seq.] shall be imposed on the obligee. The amount of the fee in a case which is being enforced under title IV-D must be less, on an annual basis, than the fee in a case which is not being enforced under title IV-D. Upon order of a court, the amount of the fee paid by the obligee may be collected from the obligor as past-due support.