The use of IoT may increase the quality of life among persons with disabilities, persons with age-related disabilities and those with specific needs when properly designed. There are many possible IoT services in various environments that provide accessibility services as well. The IoT also can be used to create tools for persons with many types of disabilities and specific needs, including physical, visual, hearing and cognitive disabilities. IoT services interact with a user through the user interface. To ensure an IoT service is accessible, the user interface must be accessible. An accessible user interface must take into account a user's physical, audio and visual capabilities and consider compatibility with any assistive technology used by the user. This Recommendation outlines essential requirements that a user interface must consider in order to secure the accessibility of smart applications.