Dear Rajsekar ji,
Answer to your query you can find in any many discussions we had earlier. Still I am giving it for your ready reference.
As regards to PF:
On reaching 20 and more employees (head counts irrespective of salary limit).
As regards to ESI:
In all states & U/T other than Maharashtra, HP & Assam- On reaching 10 and more employees (head counts irrespective of salary limit).
In Maharashtra, HP & Assam- in factory 10 & more coverable employees & in establishment other than factory 20 and more coverable employees.
As regards to Gratuity:
On reaching 10 and more employees.
PF & ESI, definition of employee includes contractor's employees also.
Gratuity, contractor's employees are included. No registration of establishment under it.
Value addition to above will be appreciated.