How can an employer know whether or not its retirement age can be objectively justified?
Ultimately it is for an employment tribunal to decide whether or not a compulsory retirement age is justified, based on the facts of each individual case. However, the law is clear about what is required. To justify a compulsory retirement age the employer must be able to show that it is a proportionate means of achieving a legitimate aim. In R (Elias) v Secretary of State for Defence  IRLR 934, the Court of Appeal explained that this means that:
- the objective of the measure in question must correspond to a real need;
- the means used must be appropriate and necessary to achieve that objective; and
- it is necessary to weigh the need against the seriousness of the detriment to the disadvantaged group.
The aims of a compulsory retirement age usually include:
- intergenerational fairness, for example facilitating access to employment by young people or sharing limited opportunities to work in a particular profession fairly between the generations; and
- dignity, ie avoiding the need for divisive disputes about employees' capacity or underperformance.
Both of these have been recognised as legitimate.
The employer has to justify having a compulsory retirement age at the particular age that it has chosen. In Seldon v Clarkson Wright & Jakes (no 2)  IRLR 748 EAT, the Employment Appeal Tribunal (EAT) was required to consider whether a retirement age of 65 was justified or whether a higher age such as 68 or 70 should have been selected as being less discriminatory. The EAT accepted that the evidence on this point may not always be as strong and compelling as it is in other areas, in part because of the "inevitable spectrum of speculation around the effect of altering the age from one figure to another". It said that concepts such as retention and workforce planning depend on "assumptions and estimates as to how people will act or react, not in general labour force terms such as might be the subject of expert evidence … but in relation in particular to the personalities and practice with which a firm is concerned". In this case, the EAT held that the chosen retirement age of 65 was proportionate.