Dear Madhu/ Milind,
Gratuity Act does not limit the maximum amount that a person can receive in the form of gratuity. Payment of Gratuity Act 1972 Sec. 4 (5).
It says that employer can cap his liability to a maximum of Rs. 3.5 lakh per employee but nothing in the law prohibits him to provide better benefit than the one mentioned.
Though the Income Tax Act says that as long as the Gratuity amount is not exceeding 8.33% of employees annual salary, its not taxable even if it crosses 3.5 lakh limit (Ref. Income Tax Act RR 98 to 111)
There are companies who pay gratuity without cap i.e. an employee can accumulate gratuity as long as he work, even if he crosses 3.5 lakh limit.