There is no fee to apply. Your organization should submit their request to us using MyTax Illinois or at the address located at the end of this section.To find out if you qualify, write a letter of request to the Illinois Department of Revenue, Sales. To be taxexempt under section 501(c)(3) of the Internal Revenue Code, an organization must be organized and operated exclusively for exempt purposes. File IRS Tax-Exempt Status Application for Recognition of Exemption. A tax exempt organization may need a letter to confirm its taxexempt status or to reflect a change in its name or address. In this article, we will focus on applying for taxexempt status for 501(c)(3) organizations in Illinois. This includes income, sales, and real estate taxes. There is no application form. You send a cover letter to the IL Department of Revenue, written on your organization's letterhead, requesting the tax exemptions.