A stipulation is an agreement among parties intended to establish one or more operative facts in a proceeding. The commission encourages parties to enter stipulations of fact. The parties to any proceeding or investigation before the commission may agree to all of the facts or any portion of the facts involved in the controversy. The parties to a stipulation may file it in writing or enter it orally into the record. A stipulation, if accepted by the commission, is binding on the stipulating parties. The parties may present the stipulation as evidence at the hearing. The commission may reject the stipulation or require proof of the stipulated facts, despite the parties' agreement to the stipulation.