applicability of PF

Hi,

I would like to know the provisions of PF Act in following circumstances:

1. Employees of the company drawing basic salary exceeding 6500 makes a declaration for non deduction of PF from salary.

- declaratin is void, deduction mandatory

2. Employees of the company drawing basic salary not exceeding 6500 makes a declaration for non deduction of PF from salary.

 declaration void if contributing members are less than 20, valid if over 20

If they can make declaration then in which form this declaration is to be made?