The Illinois Department of Revenue (IDOR), in conjunction with the Internal Revenue Service (IRS), accepts electronically filed business income tax and individual income tax returns as part of the IRS Modernized e-File (MeF) Program. MeF is a web-based system that allows electronic filing of tax returns through the Internet. MeF uses the widely accepted Extensible Markup Language (XML) format.
Linked (combined) federal/state filings and unlinked (state-only or state standalone) returns, along with payments (estimated payment(s), extension and tax payments) are allowed to be filed through MeF. The Illinois MeF program will accept and process three years of business income tax returns on a rolling calendar basis.
All entities wishing to participate must register with the IRS and be accepted in order to participate in MeF. Software developers are required to register and test their product with IDOR. Software developers must submit Form IL-8633-B, Business Electronic Filing Enrollment, to register or update registration information. Software developers are required to test their product and have it approved by Illinois. Software developers should call 217-524-4770 when they are ready to begin testing or have questions.
http://tax.illinois.gov/LegalInformation/regs/part760/760-100.pdf- Beginning with returns required to be filed for taxable years ending on or after December 31, 2011, any taxpayer required to file its federal income tax return by electronic means is required to file its equivalent Illinois income tax return for the same taxable year by electronic means. This subsection (c)(4) does not require electronic filing of amended returns or of returns of individuals or estates, or to any return the Department has announced cannot be filed by electronic means.
In the event that you are required to file electronically for federal purposes and the Illinois MeF program does not support your return type, you are exempt from the requirement until such a time that we are prepared to include your return type. See the current list of business income tax MeF forms and schedules accepted to determine if your return type is included in the program. Illinois MeF does not support any amended returns. Therefore, these returns are exempt from the requirements.