File the articles of organization In order to obtain an Illinois tax identification number, you must first file the articles of organization for your company with the Illinois Secretary of State. The Illinois Secretary of State provides an articles of organization pre-printed form on their website (see Resources).
Choose a method of filing for an Illinois tax identification number. The Illinois Department of Revenue accepts Illinois Business Registration Applications online or by mail. If applying online, use the Illinois Business Gateway website (see Resources). If filing by mail, you must use Form REG-1 (see Resources).
Fill out the Illinois Business Registration Application. Provide your company’s federal employer identification, the name of your business and its primary business address and mailing address. Indicate that your company is an LLC and how the IRS has classified your LLC for federal taxation purposes. Provide the identification number provided to your business by the Illinois Secretary of State. Indicate whether your business is part of a unitary group and if it is, provide the contact information for the designated agent -- the person who files your tax returns. Provide the names and addresses of all managers and members. Describe the activities of your business and indicate whether your business will have employees. Check any type of business activity in which your business will engage. If your company will be engaging in liquor warehousing, download and attach Schedule REG-1-L (see Resources). Indicate whether you are attaching REG-1-O or REG-1-L. Sign and date the Illinois Business Registration Application.
File your Illinois Business Registration Application. There is no filing fee. If you are filing online, follow the on-screen directions for submission. If you aren't filing online, the mailing address is Central Registration Division, Illinois Department of Revenue, PO Box 19476.