Further to the advice of Mr Varghese Mathew, I may add a few more points for the benefit of those HR Managers, who are not having in depth knowledge about the provisions in the Industrial Disputes Act 1947.
Lay Off is defined in Section 2 (KKK) of ID Act 1947
Lay off means the failure, refusal, or inability of an employer on account of shortage of coal, power or raw materials or the accumulation of stocks or the breakdown of machinery or natural calamity or for any other connected reason to give employment to a workman whose name is borne on the muster rolls of his industrial establishment and who has not been retrenched.
Retrenchment is defined in Section 2 (oo) of the ID Act 1947
Retrenchment means the termination by the employer of the service of a workman for any reason whatsoever, otherwise than as a punishment inflicted by way of disciplinary action, but does not include –
(a) Voluntary retirement of the workman; or
(b) Retirement of the workman on reaching the age of superannuation if the contract of employment between the employer and the workman concerned contains a stipulation in that behalf; or
(bb) termination of the service of the workman as a result of the non-renewal of the contract of employment between the employer and the workman concerned on its expiry or of such contract being terminated under a stipulation in that behalf contained therein; or
(c ) Termination of the service of a workman on the ground of continued ill-health.
The Provisions of Lay Off and Retrenchment are given in Chapter VA and Chapter VB of the ID Act 1947. The applicability of Chapter V-A or V-B is depending upon the number of workmen employed in the preceding calendar month / preceding twelve months.
For further details, please read Section 25C, 25D, 25E, 25F, 25G, 25H, (Chapter V-A) and 25M, 25N, and 25Q (Chapter V-B) of Industrial Disputes Act 1947