Gratuity Query in case of company name change in between service?

In one organization, if one employee joined on 15th June 2012 with XYZ Co.'s appointment letter, then that company is known as ABC, and he received the appointment letter with ABC's letterhead, where his joining date is 2nd May 2013. Now this employee is resigning from his post, and his last date of working will be 20th Feb 2018. Is he eligible for Gratuity? Kindly provide guidelines for this case.

Can you elaborate on the transition of the company's name from XYZ to ABC?

Depends on the second appointment order. If the service continuity (earlier from 15th June 2012) is taken care of, in the second appointment (normally by a change of management, do mention a clause about the service continuity), he has completed five years of continuous service and is eligible for Gratuity. If the clause is not mentioned, you are not eligible. You should have clarified at the time of receiving the ABC appointment order. However, if you have proper evidence and you could adduce before the Controller under the Payment Of Gratuity Act that both XYZ company and ABC company are one and the same and the owners/proprietors/directors are the same, and the name of the company has been changed for other reasons, you may have the case to your advantage.