It is important to note that after the conclusion of a KBA, both the employer and the union are required to respect this agreement. Therefore, an employer should retain the assistance of a lawyer before participating in collective bargaining. A collective agreement is a written contract between an employer and a union representing workers. The KBA is the result of a broad negotiation process between the parties on issues such as wages, hours and terms of employment. Illegal matters that would be contrary to a law are prohibited, such as closed shops (when an employer hires only members of a union) or illegal discrimination. SHRM`s HR Knowledge Advisors provide instructions and resources to help members respond to their HR queries. There are three different categories of subjects that are part of a CBA: compulsory, voluntary or permissive and illegal materials. Mandatory themes are the themes prescribed by law and the National Labor Relations Board (NLRB). These topics include issues such as wages, overtime, bonuses, claim procedures, safety and work practices and seniority, as well as dismissal, revocation, recall or disciplinary procedures. Voluntary or permissive issues may be negotiated, but they are not necessary and include issues such as internal union affairs and the cooperation of the employer`s board of directors.