The situation you have explained is being faced by several industries. On one hand, employees desert their employment and leave without proper intimation. On the other hand, we find companies giving offer letters and not offering employment as promised in the offer letter. During campus interviews, some educational institutions do not permit candidates who have already been given offer letters to attend interviews with other employers who come to the campus. As a result, the candidate who has the offer letter is left stranded when the company that gave him the offer letter does not offer him employment as promised.
You can write to him stating that the offer letter given to him stands canceled as he failed to join on the date mutually accepted. In the future, you can incorporate a clause in your offer of employment that in case an employee does not join on a pre-agreed date, the offer will stand canceled.
Your advice to the employee in writing, in my opinion, will be futile. Maybe during the interview process, you need to ascertain his real interest. This is easier said than done but not impossible. Probing the candidate thoroughly during the interview process will yield some results.
Questions to Consider During the Interview
a) You have worked in Chennai all along, what is the reason for your accepting to join us in Hyderabad?
Reason for this question: The candidate is from Chennai and had prior experience. A cursory glance at his past employment career will throw some light. If he had not moved out of Chennai, his probability of moving to a newer location is quite remote unless he is without employment.
b) Have you attended any interviews in the recent past?
Reason for this question: If he had attended any interviews at the time you were interviewing him, particularly in Chennai, the probability of his joining you if he received an offer from the other employer in Chennai is bleak.
c) Assuming you get an offer from the Chennai-based company and you already have an offer from our company? Which one will you choose, considering the fact Chennai is your hometown?
Reason for this question: The salary increase offered by your company when compared to the offer he probably received from yet another employer presumably in Chennai, even if it was relatively lesser, will also be a cause.
d) As you are the only son on whom your parents are dependent, is it possible that your parents will discourage you from taking up this employment? If no, do you have plans to bring them to Hyderabad so that they are comfortable?
Reason for this question: If he were the only son and if he was emotionally attached to his parents, then the likelihood of his taking up employment in Hyderabad is unlikely.
Generally, at the time of the interview, the candidate will not expect these questions, and the chances of his giving you the real information are possible. Moreover, if he does not give you a convincing reply, then you can make your own judgment.
In my opinion, companies are in a haste to fill up vacancies and seldom do they probe the chances of the candidate staying in the company long enough. I do not mean that the candidate needs to serve you for his lifetime, but the duration of his stay must be long enough.
Job sites and consultants who do not follow ethics (picking up candidates placed by them in one organization to another for monetary benefits) are generally the causes for high attrition, in my opinion.
If companies are cautious in offering positions to candidates who have stayed long enough in their past employments, then this phenomenon of rapid migration will come down.
Regards.