https://tincheck.com/
TINCheck provides everything you need for fast, secure TIN matching and identity verification including bulk TIN matching and web service API.
identity verification servicetax
https://www.irs.gov/tax-professionals/cpeo-individual-identity-verification
Information for Certified Professional Employer Organization (CPEO) applicants only. Discover how to complete the responsible individual identity verification...
internal revenue serviceidentity verificationcpeoindividual