First of all, i'm failed to understand how you are working without appointment letter. Secondly, if no contribution is been paid for you such as PF, ESIC etc from your salary then surely your employer is not counting you as an employee and must be showing you in some other category in their books. Thus you are not entitled for gratuity.
From India, Salem
1. If your establishment was employing 10 or more employees, the establishment is covered under Payment of Gratuity Act 1972.
2. Appointment letter is not a precondition, even if you did not have any appoint letter from the firm, it does not meen that you were not employed, your bank records are sufficient proof of your employment.
3. Hope you had completed a minimum tenure of 4 years & 8 months for being eligible to get gratuity.
4. In case all above conditions are fulfilled, your employer is under obligation to pay you and you have legal right to claim.
5. If your employer refuses to pay, please contact authorities in the Labour Department.
From India, Thane