In addition to the valid points brought out by Shailesh Parikh, I may add that labor laws, being welfare legislations, have imposed various statutory obligations on the employer, such as the payment of P.F., ESI, and the provision of various amenities to employees, and these are mandatory. Thus, it is necessary to identify who this "Employer" is to fix accountability for compliances. Therefore, it is necessary to issue an appointment letter by the employer. In the absence of which, it is likely to become a disputable issue, more so in the case of contractor workers since there is a principal employer also who needs to be distinguished from the employer (immediate employer) with reference to his rights and obligations under the Contract Labour Act.