The Illinois Department of Revenue (IDOR) sends letters and notices to request additional information and support for information you report on your tax return. LLC effective date is the date your LLC goes into existence.Can be the day your LLC is approved or you can future date your LLC filing. In this article, we present a collection of email examples that customer service agents can use to gather customer feedback. Be courteous and informative in your communication. Please mark the effective date of change. All Illinois Courts must accept these forms. The due date for filing your 2023 Form IL-1040 and paying any tax you owe is April 15, 2024. You can ask your landlord to lower your rent. This is called an "interim recertification.