The Internal Revenue Service is the nation 's tax collection .cy and administers the Internal Revenue Code enacted by Congress..Business Use of Car, Topic No. 510. Business Travel Expenses, Topic No. 511. Business Entertainment Expenses, Topic No. 512. Work-Related Education Expenses, Topic No. 513. Employee Business Expenses, Topic No. 514. Casualty, Disaster, and Theft Losses Including Federally Declared Disaster Areas , Topic No..Telephone and Localistance. We experience very high volumes, especially during filing season. If your issue cannot be resolved online, use the appropriate telephoneistance line..IRS Taxpayeristance Centers - when you need to talk with the IRS face-to-face. Click on your state for office locations, hours of service and other local information. For information on where to send all written correspondence, please click below on "where to file"..