Is PF a non-mandatory thing? Can some companies opt not to pay PF?

I have got a query; please help -
If your work-ex is like this -
Comapny A - Work for 4-5 months. Get you PF a/c and Tax deducted as per rule. This comapny also has a bond which is not paid. No work-ex certi taken as well.
Comapny B - Work for 14 months. Get your work-ex certi and all but this company niether deducts tax nor deducts PF.
Company C - Has to joined very soon.
In any case does not being on the legally correct side for Company A will affect Cmpany C's recruitment from three perspectives - Tax ; PAN no ; PF a/c. 'C' doent know tht emplyoee worked for 'A'

dear all,
an employee can contribute more than 12% voluntarily for PF. but, whether there is any limit on the contribution? as per my knowledge it is 20% max..plz check whether it is correct or not.
regards,
Sumit

Dear Ratii,
As per my knowledge and understanding, employee should go for it, it definately decreases the inhand but good when an employee gets a lumpsum amount at the end of his/her emploment.
So if we see the long term prospective, it is always beneficial for employees to get it deducted from the salary.
Hope my answer will satisfy your querry.
Tk care n best wishes
Regards
Ditti