As of Dec. 24, 2025, the USPS updated its postmark rules. A postmark will not be applied the day you mail something or drop it off at the post office. It will reflect the date of the first automated processing operation, which could be days later. Because the Indiana Department of Revenue (DOR) uses the postmark to determine timeliness, a mailing delay could lead to late fees, penalties, or interest.
The best way to pay and respond: INTIME
To avoid postal delays entirely, use Indiana’s secure online portal, INTIME. Electronic submissions are instant and provide immediate confirmation of receipt.
1. Make a payment
- Bank Account (Free): Pay via Automated Clearing House (ACH) with no transaction fees.
- Credit/Debit Card: Submit payments for a small processing fee.
- Locate the “Payments” panel on INTIME’s homepage and select “Make a payment.” You will need your Social Security Number (SSN) or Letter ID.
2. Respond to Letters or Notices
- Upload documents: Directly submit requested documents through INTIME.
- Locate the “Respond to correspondence” panel on the main page. You will need the Letter ID from the correspondence you received.
If you must use the mail
If you choose to mail your return or payment, take these steps to ensure it is considered timely:
- Request a manual postmark: Present your mail piece at a USPS retail county and specifically request a “manual (local) postmark.” This aligns the postmark with the date the USPS took possession.
- Mail early: USPS recommends mailing items at least one week before the deadline to account for possible processing delays.
- Use Certified Mail: For proof of mailing, use Certified or Registered Mail to obtain a dated receipt.
Additional Resources
- Payment Plans: Find information on monthly installments or money order instructions on the DOR payments & billing page.
- USPS rule details: Read the full rule on the Federal Register's official webpage.