Iowa Admin. Code r. 621-6.1
The scope of negotiations shall include the mandatory subjects of collective bargaining as provided in Iowa Code section 20.9. "Permissive" matters are all other subjects upon which bargaining is not prohibited. Either party may introduce permissive matters for negotiation, and negotiation on these matters may continue until resolved by mutual agreement of the parties or until negotiations reach the arbitration stage of impasse; however, no party is required to negotiate on permissive subjects of bargaining. Unresolved permissive matters shall be excluded from arbitration unless submission of the matter has been mutually agreed upon by the parties. Such an agreement is applicable only to negotiations toward the collective bargaining agreement then sought and is not binding upon the parties for future negotiations.
Iowa Admin. Code r. 621-6.1