Illinois Tax Postmark Changes Could Impact Filings
Summary
The Illinois Department of Revenue (IDOR) has issued a notice regarding changes to United States Postal Service (USPS) postmarks that could impact tax filings in 2026. The USPS postmark may no longer reflect the actual drop-off date, potentially affecting time-sensitive documents like tax returns and payments.
What changed
The Illinois Department of Revenue (IDOR) has alerted taxpayers to potential impacts from changes in United States Postal Service (USPS) postmark procedures, effective in 2026. While the postmark will still indicate the date of first automated processing, it may not reflect the actual date mail was deposited. This change is significant for time-sensitive submissions such as tax returns and payments, as the official postmark date is often used to determine timely filing.
Regulated entities, particularly those in Illinois, should be aware that relying solely on the postmark date for proof of timely filing may become problematic. Taxpayers should consider alternative methods for ensuring timely submission, such as using certified mail with return receipt, electronic filing, or dropping off documents directly at IDOR offices if feasible. The IDOR has provided an informational bulletin (FY 2026-17) for further details on this developing issue.
What to do next
- Review Informational Bulletin FY 2026-17 for details on USPS postmark changes.
- Advise clients and internal teams on potential issues with postmark dates for tax filings.
- Consider alternative methods for ensuring timely filing, such as electronic submission or certified mail.
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Scam Alert: Fake Texts and Websites Impersonating IDOR
Be alert for fraudulent messages or websites attempting to steal your banking information, login credentials, or credit card details. The Illinois Department of Revenue (IDOR) will never request personal or financial information via text message. To confirm official communications or contact details, always visit https://tax.illinois.gov.
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FY 2026-17, Changes to United States Postal Service on Postmarks Could Impact Illinois Tax Filings
News – Tuesday, January 27, 2026 print Email The United States Postal Service (USPS) has announced changes to postmarks that could impact tax filings in 2026. While the USPS postmark will still show the date of the first automated processing operation, the postmark may no longer reflect the date when the piece of mail was dropped off at a local post office. This change can directly impact time-sensitive documents such as tax returns and payments.
See Informational Bulletin FY 2026-17, Changes to United States Postal Service on Postmarks Could Impact Illinois Tax Filings for more information.
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