In most cases, employers must not compel employees to retire or have a default retirement age, unless setting a retirement age can be objectively justified for that particular role.
You must take care in your discussions, to not make a person feel like you are putting them under pressure to retire. Therefore, do not ask "when/are you looking to retire?", unless the employee brings up the subject of their imminent retirement.
In performance appraisals, do not assume that a person is not interested in training or development, due to their age.
You must not assume that if an employee indicates that they plan to retire at a particular time, he/she will do, until the employee has provided formal written notice of their retirement (you can use the Retirement Notification Form for this). Conversations about an intention to retire, are not binding on an employee.
Be very careful not to discriminate against people because of their age, whether directly, or indirectly.