Only a simple letter stating the organisation is closing down will suffice. But before you send an intimation to the authorities please ensure the following, so as to avoid any future hassels :-
1. Contribution of employee as well as employer is deducted and deposited till the date of closing of the organisation and the copy of challan is attached with the letter.
2. If there are any contractors then ensure that the conractor also complies with the contribution requirements. Issue for VI-B to the contractor and intimate the labour department too.
3. If you are a manufacturing set-up then also enclose the copies of surrender of factory license and in case you are an establishment under shops and establishment then the registration certificate . Also surrender the Contract Labour Registration Certificate etc.
6th June 2013 From India, Mumbai