Hi Keerti,
CTC is defined as total cost incurred by the company on an employee. Obvious expenses are Monthly Salary, Bonus, Employer's contribution towards his PF. Then you can add gratuity (Which company will be required to pay to an employee who has served for at least 5 yrs @ half month's salary for each completed year of service) To include this in the CTC, one may divide 2 and half times salary by 60 and add it to the monthly CTC. The management may also include expenses like transportation, telephone bill, subsidised food etc to this list of COST which company is incurring on the employee.
Hope that clarifies.
Regards,
Naresh Taneja