29 C.F.R. § 1605.3
(b) Inquiries which determine an applicant's availability to work during an employer's scheduled working hours.
(2) As a result of the oral and written testimony submitted at the Commission's Hearings on Religious Discrimination, discussions with representatives of organizations interested in the issue of religious discrimination, and the comments received from the public on these Guidelines as proposed, the Commission has concluded that the use of pre-selection inquiries which determine an applicant's availability has an exclusionary effect on the employment opportunities of persons with certain religious practices. The use of such inquiries will, therefore, be considered to violate title VII unless the employer can show that it:
(ii) Was otherwise justified by business necessity.
Employers who believe they have a legitimate interest in knowing the availability of their applicants prior to selection must consider procedures which would serve this interest and which would have a lesser exclusionary effect on persons whose religious practices need accommodation. An example of such a procedure is for the employer to state the normal work hours for the job and, after making it clear to the applicant that he or she is not required to indicate the need for any absences for religious practices during the scheduled work hours, ask the applicant whether he or she is otherwise available to work those hours. Then, after a position is offered, but before the applicant is hired, the employer can inquire into the need for a religious accommodation and determine, according to the principles of these Guidelines, whether an accommodation is possible. This type of inquiry would provide an employer with information concerning the availability of most of its applicants, while deferring until after a position is offered the identification of the usually small number of applicants who require an accommodation.