An employer is not required to make an accommodation if it would impose an "undue hardship" on the operation of the employer's business. "Undue hardship" is defined as an "action requiring significant difficulty or expense" when considered in light of a number of factors. These factors include the nature and cost of the accommodation in relation to the size, resources, nature, and structure of the employer's operation.
Undue hardship is determined on a case-by-case basis. Where the facility making the accommodation is part of a larger entity, the structure and overall resources of the larger organization would be considered, as well as the financial and administrative relationship of the facility to the larger organization. In general, a larger employer with greater resources would be expected to make accommodations requiring greater effort or expense than would be required of a smaller employer with fewer resources.
If a particular accommodation would be an undue hardship, the employer must try to identify another accommodation that will not pose such a hardship. Also, if the cost of an accommodation would impose an undue hardship on the employer, the individual with a disability should be given the option of paying that portion of the cost which would constitute an undue hardship or providing the accommodation.
For additional information, take a look at the following resource:
Fact Sheet: Reasonable Accommodation in the Workplace