Dear P. Itikirala,
For gratuity calculation, the formula is Number of years of service x last drawn salary x 15 / 26.
1. Number of years of service: If the service comprises completed years and a fraction of a year, the fraction has to be rounded to the full year. i.e. If the fraction is 6 months or below, it will be rounded down. And if it is above six months, it will be rounded up.
2. Last drawn salary: Practically, it is advisable to take the average salary of the preceding twelve months.
For example: Let the service be 26 years and the salary be Rs. 20,000. Gratuity calculation is = 26 x 20000 x 15 / 26 = Rs. 3,00,000.
Note: Now the ceiling limit for gratuity is Rs. 10,00,000. But if the employer wishes, he can give above Rs. 10,00,000. However, as per section 10(10) of the Income Tax Act, tax exemption is limited to Rs. 10,00,000.
Abbas.P.S