It is against the law to discriminate against, harass or victimise a person because of gender reassignment. Anyone who is proposing to undergo, is undergoing or has undergone a gender reassignment process is protected from discrimination under the Equality Act.
Also the definition of gender reassignment no longer requires the person to be under medical supervision to be protected by the law. A transsexual person also has the protected characteristic of gender reassignment.
People undergoing gender reassignment are also protected from discrimination due to absence from work. Absence because of gender reassignment should be treated no less favourably than if absence was due to sickness, injury or another reason.
Employers must ensure they have clear anti-discriminatory policies and procedures in place and should seek advice if they are in any doubt as to how to proceed.