If you received an LTR-500 letter and attached REG-1, Illinois Business Registration Application, then the department could be missing information for your account that can hold up the processing of your Certificate of Registration or the release of forms. Please fill out the attached application for your business as thoroughly as possible and submit it. If you believe that you received the letter in error, please call our Central Registration Division at (217) 785-3707, or you may contact us via email by using the "Submit a question" form at the bottom of this page.