A physiological and ultimately surgical procedure, under medical supervision, for the purpose of changing a person's sexual characteristics. The process is undertaken by transsexual persons. A transsexual is a person who firmly believes that he or she belongs to the sex opposite to the sex (or gender) to which he or she was assigned by the anatomical structure of his or her body at birth, a condition known as gender dysphoria. It is important to distinguish a transsexual person from a transvestite, who merely wishes to dress in clothes of the opposite sex. Previously, under English law transsexual persons who had undergone gender reassignment were not recognized in their acquired gender, and although able to obtain some official documents in their new name and gender, they could not obtain a new birth certificate or marry in their acquired gender. Under the Gender Recognition Act 2004, a transsexual person may apply to the Gender Recognition Panel for the issue of a full Gender Recognition Certificate. Before issuing the certificate the Panel must be satisfied that the applicant has, or has had, gender dysphoria, has lived in his or her acquired gender for the past two years, and intends to continue to live in that gender until death. The certificate entitles the applicant to be legally recognized in his or her acquired gender, to a new birth certificate, and to marry in that gender. Transsexual persons who have not acquired a Gender Recognition Certificate will not be entitled to have their birth certificates amended and will still only be able to marry in the sex registered at birth. Important cases in this area include Corbett v Corbett  P 83 (HL), Goodwin v UK (App no 28957/95) (2002) 35 EHRR 18, and Bellinger v Bellinger  UKHL 21,  2 AC 467.
Initially discrimination in the workplace with respect to a person's sexual orientation or transsexualism was outside the ambit of the Sex Discrimination Act 1975 (see sex discrimination). The definition of sex within that Act referred to discrimination on grounds of biological gender and hence covered discrimination only between men and women. As a result of a series of cases before both the European Court of Justice and the European Court of Human Rights, the UK Sex Discrimination Act now includes transsexualism within its definition. As gender reassignment is an ongoing process, regulations have been issued clarifying the protections to be given at the workplace to a transsexual undergoing this process. The Sex Discrimination (Gender Reassignment) Regulations 1999 bring UK law into line with the decision of the European Court of Justice in Case C-13/94 P v S and Cornwall CC  IRLR 347, in which discrimination on grounds of gender reassignment was ruled to be contrary to European Community law.
The Regulations provide protection against discrimination by employers at all stages of the reassignment process, starting when an individual indicates an intention to begin reassignment. The Regulations also cover recruitment procedures, vocational training, and discrimination with respect to pay (see equal pay). The Sex Discrimination Act as amended by the Regulations outlaws direct discrimination and provides for employees who are absent from work to undergo treatment to be treated no less favourably than they would be if the absence was due to sickness or personal injury. The protection is extended to postoperative treatment on a transsexual's return to work. Transsexuals are also protected from harassment. There is a defence to a complaint of less favourable treatment if being a man, or a woman, is a genuine occupational requirement for the employment in question. In addition, there are further supplementary exceptions, some of which apply only temporarily while the process of reassignment is continuing. One exception is where the job is likely to involve the holder of the job being called on to perform intimate body searches pursuant to statutory powers (e.g. a police officer). In that case, however, the employer must take into account whether there are already enough employees who are capable of carrying out those duties whom it would be reasonable to employ on those duties. In no case will less favourable treatment be justified under the exceptions where the individual concerned has acquired a Gender Recognition Certificate under the Gender Recognition Act 2004. This allows for legal recognition of the acquired sex, and the person must be treated as being of that sex for all purposes (Goodwin v UK (App no 28957/95) (2002) 35 EHHR 447; Case C-117/01 KB v National Health Service Pensions Agency  IRLR 240 (ECJ).