Generally, proceedings to establish and enforce child support obligations operate prospectively from the date of commencement of support proceedings. However, in an action under the Uniform Parentage Act, a court may determine liability and enter orders for reimbursement of past support provided by the custodian to the child. In re Marriage of Smith, P.2d, 1999 Colo ; People in Interest of A.A.V., 815 P.2d 997 (Colo. App. 1991). The child support debt must be based on the amount of child support due under the current child support enforcement guidelines then in effect multiplied by the number of months the family received public assistance. Also, the total amount of child support debt shall not exceed the total amount paid through public assistance. Section 14-14-104(1)(b), C.R.S. 1999. Thus, under 14-14-104(1)(b), an obligor is liable to the county department of social services (department) for an amount not exceeding the full amount of public assistance paid during the period when no order for child support existed. This provision may expose a responsible parent who had not been subject to an initial order to the same liability that would have resulted if there had initially been a court order directed to that parent pursuant to 14-14-104(1)(a), C.R.S. 1999. Cf. In re Marriage of Ward, 856 P.2d 67 (Colo. App. 1993) (under prior version of 14-14-101(1)(b), court must establish child support debt in an amount equal to or greater than the amount of public assistance paid). The parent's financial resources, including current child support obligations, are pertinent in devising a schedule for repayment of the public assistance debt, and the trial court may order that such payment commence after the obligation to pay current child support has expired. In re Marriage of Ward, supra.