Okay!!!
I do appreciate obtaining ECR from the contractor. With these procedures, we can confirm that they made the payment to particular employee. But, for eg., if the contractor has 10,000 or more employees (like G4S or ISS) in all over India, their PF contribution is from one location (eg., gurgoan or patna) and only 3 employees are working with you (say, in Chennai), then, I think ECR collection (which contains the details of 10,000+ employees) will be unnecessary time consuming work.
During Statutory Audit, the physical documentation is only valid, like Screenshot of "IP Mapping" in ESI and "Para 36B Proforma" for PF along with paid challans. Self developed excel sheets may be useful for tracking but it can't be a statutory document..
Please correct me, if I'm wrong...