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E-filing information for 1120 Illinois

Electronic filing mandate

Any taxpayer required to file their federal income tax return electronically, is required to file an equivalent Illinois income tax return for the same taxable year electronically, per Title 86, Part 760, Section 760.100(c)(4). This subsection (c)(4) doesn’t require you to electronically file amended returns, returns of individuals or estates, or any return the department announced you can't electronically file.

Returns supported for electronic filing

You can electronically file the following return types:
  • C Corporation
  • S Corporation
  • Estimates
  • Extension
  • Consolidated/Combined
  • Short year (ending after December 26)
  • Unitary (with no passthrough members)

Returns not supported for electronic filing

You can't electronically file the following return types:
  • Amended returns
  • Returns with late interest, failure to file penalty, and failure to pay penalty
  • Unitary returns with Partnership or S Corporation members
  • Power of Attorney
  • Foreign corporations
  • Annual report

Signature requirements for electronic filing

Illinois doesn’t have a specific signature form for corporate returns. Instead, Illinois considers the signature date you enter on the
ILELF
 screen and the act of completing and filing electronically an authorized signature.

Resubmit returns

If you need to make a change to a return that you have already electronically filed, and Illinois has already accepted it, amend and paper file the return.
If Illinois rejects a Business Income Tax return filed timely through
MeF
, you'll need to resubmit and have Illinois accept the return within 10 calendar days after you initially received the rejected acknowledgment to avoid penalties. Perfection for electronic retransmission is generally required when the original return had errors in the XML format or errors that caused that return to fail Illinois e-file schema validation or business rules.

Attachments

Illinois requires a valid federal attachment in the electronic file. Therefore, if the federal return is not supported for electronic filing by the IRS, you can't e-file the state return.

Payment methods

The Illinois DOR accepts direct debit (EFW), electronic funds transfer (EFT) or paper check/money order for balance due returns and estimates. If you file an extension electronically, you need to pay via Electronic Funds Withdrawal (EFW).
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