If my corporation or LLC is in another state, will I need to register in Tennessee?

Yes. You would need to contact the Tennessee Secretary of State https://sos.tn.gov/ (615 741-2286) You may obtain forms to register as a foreign corporation or limited liability company and check for name availability. To obtain a business tax license, contact the Department of Revenue. Federal Employee Identification Numbers (FEIN) may be obtained from the IRS https://www.irs.gov/.