Schedule 9 Part 1 Occupational requirements
General
1(1)A person (A) does not contravene a provision mentioned in sub-paragraph (2) by applying in relation to work a requirement to have a particular protected characteristic, if A shows that, having regard to the nature or context of the work—
(a)it is an occupational requirement,
(b)the application of the requirement is a proportionate means of achieving a legitimate aim, and
(c)the person to whom A applies the requirement does not meet it (or A has reasonable grounds for not being satisfied that the person meets it).
(2) [lists provisions that bar discrimination based on protected characteristics]
(3)The references in sub-paragraph (1) to a requirement to have a protected characteristic are to be read—
(a)in the case of gender reassignment, as references to a requirement not to be a transsexual person ...........;
(b)in the case of marriage and civil partnership, as references to a requirement not to be married or a civil partner..........
Explanatory Note:
787.This paragraph provides a general exception to what would otherwise be unlawful direct discrimination in relation to work. The exception applies where being of a particular sex, race, disability, religion or belief, sexual orientation or age – or not being a transsexual person, married or a civil partner – is a requirement for the work, and the person whom it is applied to does not meet it (or, except in the case of sex, does not meet it to the reasonable satisfaction of the person who applied it). The requirement must be crucial to the post, and not merely one of several important factors. It also must not be a sham or pretext. In addition, applying the requirement must be proportionate so as to achieve a legitimate aim.
This Schedule does not provide an exemption for preferentially employing a trans or married person, because the exemption is not needed. It's already legal to discriminate against 'cis' people and single people, because they don't have a protected characteristic.