IRS refers to the Internal Revenue Service which is used for collecting the taxes in United States. Internal Revenue Service is a government organization and is a part of the Department of the Treasury. IRS is also liable for enforcing and interpretation the Internal Revenue Code. Its original name was given in 1918 and its headquarters located at Washington, D.C., United States. The contact details like address, contact number, customer care number and customer service phone number of Irs Oklahoma is displayed above.