For closing down a company which has had an employment strength of 50 or more employees, a 'simple' letter will not be sufficient but it is to be prepared in accordance with the provisions of the Industrial Disputes Act. Since by closure of the company the employees will become jobless they will have to be given notice in advance (at least one month) or paid notice pay in lieu of notice and they should also be paid retrenchment compensation at the rate of 15 days pay for every completed year of service. This is in addition to gratuity payable under the Payment of Gratuity Act.
Attached please find the form Q which is to be sent to Labour Authorities informing the closure of the company. The same is used to inform the employees also. Hope the same would be useful to you.
Regards,
Madhu.T.K