The rules of the scheme define who is eligible to join the scheme and when. Common rules include the following:

a minimum entry age, e.g. 18 or 21;

a probationary or ‘waiting’ period before an employee may join the scheme – commonly set at one year, though it may be longer for those below a certain age;

differentiation between categories of employee, e.g. a scheme may differentiate between management, staff and workers;

a different level of benefits offered to each category, e.g. more generous benefits are provided to the management category.