The American with Disabilities Act (ADA) applies to all employers with 15 or more employees. This includes private employers, state and local governments, employment agencies and unions. The ADA makes it illegal to discriminate in the job application procedures, hiring, firing, advancement, compensation, job training and any other terms and conditions of employment. Employers also must make reasonable accommodations so that disabled employees can perform the essential duties of their jobs. This requirement makes a strong argument for the significance of job descriptions and the need to make sure they are accurate. Without written documentation about what the essential duties of a job are, the employer can have a more difficult time justifying if they are considering something to not be a reasonable accommodation.