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Individual Income Tax

What is a Letter ID?

A Letter ID is a unique set of letters and numbers used to identify each letter issued by IDOR. To obtain access to an Individual Income Tax account through MyTax Illinois, you are required to enter a Letter ID from a letter that was issued within the last 90 days from your Individual Income Tax account. Common letters that can be used to activate your account include:

  • Return Correction Notice
  • Notice of Tax Due
  • Notice of Deficiency
  • Notice before Collection
  • Examiner’s Report
  • Notice of Proposed Tax Due
  • Certain IDOR Collections notices

If you do not have a letter that meets these criteria, you can request a Letter ID be mailed to you using the “Request a Letter ID” link on the Individuals panel of the MyTax Illinois homepage.

What if my Letter ID does not work?

For joint filers, the Letter ID will only activate an account for the taxpayer listed first on the letter (i.e., the primary spouse). Individual Income Tax filers who file their returns jointly and who would like to file returns or respond to notices should activate a MyTax Illinois account under the person listed as the primary taxpayer. The letter must be issued within the last 90 days. If your letter is greater than 90 days old or is otherwise invalid, you can request a new letter ID under the Individuals panel on the MyTax Illinois homepage. Please note that some categories of letters, for example, a letter that contains “Identity Verification” in the letter title, cannot be used to activate an account. If you have any questions about activating a MyTax Illinois account using a Letter ID, please contact us at or call Taxpayer Assistance at 1 800 732-8866.

How do I Request a Letter ID to activate my account?

If you do not have a recent notice issued to you by IDOR from which you can obtain a Letter ID, then you can select the link “Request a Letter ID” under the ‘Individuals’ panel on the MyTax Illinois homepage. You must have previously filed a tax return with IDOR in order to activate an account. We will send a letter to the mailing address we have on file for you.

Do I have to activate a MyTax Illinois account to file my Form IL-1040, Individual Income Tax Return?

No. You do not have to activate a MyTax Illinois account to file your current year Form IL-1040, Individual Income Tax Return. For more information, see File Form IL-1040, Individual Income Tax Return, on MyTax Illinois.

Note: Make sure to have your adjusted gross income amount from your prior year return filed in Illinois, a valid Illinois Driver’s License card, or a valid Illinois State Identification card.

If you have a MyTax Illinois account, you can login to your account and choose the “File a Return” option.

Why won’t MyTax Illinois or other tax preparation programs accept my driver’s license or state ID information?

Your driver’s license or state ID information must be entered exactly as it appears on your card issued by the Illinois Secretary of State. Your 12-character license or state ID number starts or ends, respectively, with the first letter of your last name. Make sure you do not enter any punctuation after your middle initial, and do not enter an invalid suffix (valid suffixes are Sr, Jr, I, II, III, IV, etc. and are not Mr. or Ms.).

Examples of common entry errors:

  • Using a Middle Name when only a Middle Initial is shown
  • Using a Middle Initial when only a Middle Name was shown
  • Using a different weight from what is shown
  • Using a Suffix when none is shown
  • Not using a Suffix when one is shown
  • Typos

Why won’t MyTax Illinois accept my Prior Year Adjusted Gross Income (AGI)?

If your Prior Year AGI doesn’t match the Prior Year AGI on the IDOR production file, there may be:

1. No prior year return on file with IDOR. (Historic Filer). This may be because:

  • The prior year return was rejected.
  • The prior year return was filed under an incorrect SSN/ITIN.
  • The prior year return was received but was unable to be processed.
  • The prior year return had a notice issued regarding verification of identity, and no response to that notice was received by IDOR.
  • the ID is too new and is not yet in IDOR’s system

2. A change or correction was made to the return by the taxpayer or IDOR after the original filing.