Relevant portion of Act reads as follows:
The Payment of Gratuity (Amendment) Act, 1987 has prescribed provisions for compulsory insurance for employer’s liability for payment towards the gratuity under the Act from the Life Insurance Corporation of India establishment under the Life Insurance Corporation of India Act,1956 or any other prescribed Insurer. However, employer of an establishment belonging to or under the control of the Central Government or the State Government are exempted from operations of these provisions. (Section 4A)[xxiii]
So cross check whether the company has taken insurance from LIC of India or not.