Ohio Rev. Code Ann. § 4909.33

Whenever any rate, toll, charge, or service ordered substituted by the public utilities commission is a joint rate, toll, charge, or service, and the public utilities which are parties to it fail to agree upon the apportionment of such joint rate, toll, charge, or service within twenty days after the service of such order, the commission may, after hearing, make and issue a supplemental order fixing the apportionment of such joint rate, toll, charge, or service between such public utilities. Such order shall take effect of its own force as a part of the original order.