It depends entirely on your laws pertaining to employment. In Canada for instance, most provinces do not allow a former employer to discuss a person's work and performance. In Alberta, by example, all I was legally permitted to do when called for a reference was confirm the individual was under my employ for X amount of time. I could not comment on that employment. You cannot say whether the person left on their own request or was let go. I could neither recommend the past employee nor advise the potential employer seeking reference that the person was a poor candidate for hire. It is the law. Similarly, during interview, you cannot ask the candidate if they have ever been fired. This is why it is so very important for a potential employer to contact personal references. You would be surprised how many people would not recommend their acquaintance be hired.