W. Va. Code § 48-1-204: Arrearages or past due support defined.

"Arrearages" or "past due support" means the total of any matured, unpaid installments of child support required to be paid by an order entered or modified by a court of competent jurisdiction, or by the order of a magistrate court of this state, and shall stand, by operation of law, as a decretal judgment against the obligor owing such support. The amount of unpaid support shall bear interest from the date it accrued, at a rate of five percent per annum, and proportionately for a greater or lesser sum, or for a longer or shorter time. Except as provided in rule 23 of rules of practice and procedure for family law and as provided in section 1-302, a child support order may not be retroactively modified so as to cancel or alter accrued installments of support.