This characteristic provides protection for transsexual people, and is defined as applying if a “person is proposing to undergo, is undergoing or has undergone a process (or part of a process) for the purpose of reassigning the person’s sex by changing physiological or other aspects of sex”.
From this definition it is clear that it would be discrimination to treat transsexual people less favourably for being absent from work because they were undergoing gender reassignment than they would be treated if they were absent if they were ill or injured. Similarly, it is clear that there is no requirement for a person to be under medical supervision to be protected – for instance, a woman who decided to live as a man but did not undergo any medical procedures would still be covered (see the definition above where it talks of “other attributes of sex”).
Discrimination also extends to protecting a worker if you treat them less favourably based on:
•Your perception of their gender reassignment status, regardless of whether or not the perception is correct.
•Any perception you may have about the way in which other people would be influenced by someone who was or had undertaken gender reassignment.
You cannot defend a direct discrimination claim by ‘justifying’ it (arguing that your actions were a proportionate means of achieving a legitimate aim.