http://www.irs.gov/instructions/iw9/ar02.html IRS.gov: Instructions for the Requester of Form W-9 IRS Form W-9 Tax ID http://www.irs.gov/instructions/iw9/ar02.html you may need to file Form W-9 http://www.irs.gov/instructions/iw9/ar02.html already regulations permitting substitute Forms W-9 IRS.gov: Instructions for the Requester of Form W-9 already regulations permitting substitute Forms W-9 authenticates and verifies the submission https://www.irs.gov/instructions/iw9/ar02.html#d0e581 IRS.gov: Instructions for the Requester of Form W-9