The checks for PF includes asking for proof of deposit of PF on monthly basis.
Every month along with claim for pay and allowances, proof of previous month deposit of PF should be verified.
So is the case with ESIC also.Bonus payments also can be verified from time to time.
Make a check list of verifications to be done on each contractor and verify it by asking for attachment of authentic documentation along with payrolls.
16th March 2019 From India, Pune