In any contested case all parties shall be afforded an opportunity for hearing after reasonable notice. The notice shall state the time, place and issues involved, but if, by reason of the nature of the case, the issues cannot be fully stated in advance of the hearing, or if subsequent amendment of the issues is necessary, they shall be fully stated as soon as practicable, and opportunity shall be afforded all parties to present evidence and argument with respect thereto. Prior to assignment of a case to an administrative law judge as provided by sections 14.48 to 14.56, all papers shall be filed with the agency. Subsequent to assignment of the case, the agency shall certify the official record to the Office of Administrative Hearings, and thereafter, all papers shall be filed with that office. The Office of Administrative Hearings shall maintain the official record which shall include subsequent filings, testimony and exhibits. All filings are deemed effective upon receipt. The record shall contain a written transcript of the hearing only if preparation of a transcript is requested by the agency, a party, or the chief administrative law judge. The agency or party requesting a transcript shall bear the cost of preparation. When the chief administrative law judge requests preparation of the transcript, the agency shall bear the cost of preparation. Upon issuance of the administrative law judge's report, the official record shall be certified to the agency.