The ADA defines essential functions as follows:

Essential functions – The term essential functions means the fundamental job duties of the employment position the individual with a disability holds or desires. The term "essential functions'' does not include the marginal functions of the position.

A job function may be considered essential for any of several reasons, including but not limited to the following:

  1. The function may be essential because the reason the position exists is to perform that function;
  2. The function may be essential because of the limited number of employees available among whom the performance of that job function can be distributed; and/or
  3. The function may be highly specialized so that the incumbent in the position is hired for his or her expertise or ability to perform the particular function.

Evidence of whether a particular function is essential includes, but is not limited to:

  1. The employer's judgment as to which functions are essential;
  2. Written job descriptions prepared before advertising or interviewing applicants for the job;
  3. The amount of time spent on the job performing the function;
  4. The consequences of not requiring the incumbent to perform the function;
  5. The terms of a collective bargaining agreement;
  6. The work experience of past incumbents in the job; and/or
  7. The current work experience of incumbents in similar jobs



Basically, "Essential Functions" are the basic job duties that an employee must be able to perform, with or without reasonable accommodation (we will talk more about reasonable accommodations in the next section). Before advertising a job and beginning the hiring process, you'll need to create a job description which details the essential and marginal functions (non-essential functions) of the job position.  The essential job functions will need to be included in the job description.  This information will be important for determining if an applicant can perform the essential duties of the position with or without reasonable accommodation.

For example, let's look at the essential and marginal job functions of a receptionist in a professional office.picture of a receptionist

Essential job functions might include:

Marginal job functions might include:

For this receptionist position, an applicant would need to be able to perform the essential job functions with or without reasonable accommodation.  The marginal or non-essential job functions are those that could be redesigned or reassigned to other employees, if necessary. You should carefully examine each job to determine which functions or tasks are essential to performance. This is particularly important before taking an employment action such as recruiting, hiring, promoting or firing employees.

Whether or not a particular duty is considered marginal will depend on:

In summary, a duty would be considered an "essential" function of the position if it is important to your company's operation, it is performed with frequency, there isn't sufficient staff to reassign it, and it can't be redesigned or performed in another way.

The ADA regulation also states that relevant evidence as to whether a function is essential may include:

It is important to remember this message: "The employer has the right to determine the essential functions, educational training requirements, and the performance standards of the job, as long as standards and requirements are consistently applied and are not established specifically to discriminate against people with disabilities."  (Baum, et al., 2004)


 Let's look at an example of essential function through the following quiz:

Toggle open/close quiz question

A research assistant at XYZ corporation is responsible for data input and answering phones as a backup to the receptionist a few minutes a day.  Which of the following would appear to be essential functions of this job?
    a.Inputting, accessing, and retrieving data from the computer
    b.Entering information manually or visually reading information from a computer screen
    c.Answering the telephone



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