PF And ESI Returns

Dear All,
Please tell me that is it mandatory to file PF return and ESI Return on mandatory basis.
During part of audit of one of my client they told that it is not mandatory to file pf return on mandatory basis so they are not filling PF returns during the year.
Please provide me the relevant notification regarding this.
Thanks in Advance

hello
If you are enrolled with PF & ESI then it is mandatory for filing returns. Now a days we have to file online instead of manual returns

yes!
pf and esi are mandatory for filling returns.. last days we followed year ending submission of the pf report in manually prepared format but now days it is easy to submit online .
We should submit pf and esi once our concern enrolled.