If you are mailing an Illinois IL-1040, send it to one of two Springfield PO boxes depending on whether a payment is enclosed. Returns without a payment go to Illinois Department of Revenue, PO Box 19041, Springfield, IL 62794-9041. Returns with a payment go to Illinois Department of Revenue, PO Box 19027, Springfield, IL 62794-9027.1Illinois Department of Revenue. Mailing Addresses Using the wrong box routes your return to the wrong processing team and can delay a refund or a payment credit by weeks.
The Two IL-1040 Mailing Addresses
- No payment enclosed: Illinois Department of Revenue, PO Box 19041, Springfield, IL 62794-9041
- Payment enclosed: Illinois Department of Revenue, PO Box 19027, Springfield, IL 62794-9027
Both addresses come from the Department of Revenue’s official mailing page and the IL-1040 instructions.1Illinois Department of Revenue. Mailing Addresses Write out the full nine-digit ZIP. A single wrong digit can bounce your envelope between postal facilities before it reaches Springfield.
If you are sending a payment voucher (Form IL-1040-V) along with your return, use the address that matches your return type. If the voucher travels separately with its own check, send it to the “with payment” box.1Illinois Department of Revenue. Mailing Addresses
What to Put in the Envelope
The IL-1040 is the primary form for Illinois individual income tax,2Illinois Department of Revenue. Illinois Department of Revenue Individual Income Tax Return IL-1040 and a printable version is available on the Department’s website.3Illinois Department of Revenue. 2025 IL-1040 Individual Income Tax Return Before you seal the envelope, check that it contains:
- Your complete Social Security number on the form; partial numbers are not accepted2Illinois Department of Revenue. Illinois Department of Revenue Individual Income Tax Return IL-1040
- Your W-2 and 1099 forms showing income for the year
- Every supporting schedule referenced on the IL-1040, stapled together as the instructions direct
- Form IL-1040-V if you owe a balance and are paying by check or money order
When you include a check, make it payable to “Illinois Department of Revenue” and write your Social Security number on the memo line. The voucher asks for your SSN, name, address, and the exact payment amount.4Illinois Department of Revenue. IL-1040-V Payment Voucher for Individual Income Tax If the check and the return get separated during processing, the SSN on the memo line is what gets your payment credited to the right account.
Two mistakes come up often. The first is sending a return with a check to the no-payment box, which routes the check to a team that doesn’t process deposits. That lag can trigger late-payment interest even on a return mailed before the deadline. The second is forgetting to attach W-2s. The Department can still process the return, but it invites follow-up letters and holds up a refund.
Can You Use FedEx or UPS?
Not for the IL-1040. FedEx, UPS, and DHL cannot deliver to PO boxes, and PO boxes are all the Department of Revenue publishes for individual income tax returns. There is no publicly listed street address for delivering an Illinois state tax return by private carrier. If you want tracking and a delivery confirmation, USPS Certified Mail is the practical option.
Deadline and the Postmark Rule
The filing deadline for the 2025 tax year IL-1040 is April 15, 2026.5Illinois Department of Revenue. Due Date/Extension to File Income Tax Return (2025 IL-1040) Your return counts as filed on the date of the USPS postmark, not the date the Department receives it. A return postmarked April 15 and delivered April 22 is still on time.
One wrinkle to know about: USPS adopted new postmark rules effective December 24, 2025, which can affect how dates are stamped on mail dropped in collection boxes. If you are mailing close to the deadline, take the envelope to a post office counter and ask for a hand-stamped postmark rather than relying on a collection box pickup.
Illinois grants an automatic six-month extension to file; no separate form is needed. The extension gives you more time to file, not more time to pay. If you expect to owe, send payment with Form IL-505-I by April 15, 2026 to avoid penalties and interest.5Illinois Department of Revenue. Due Date/Extension to File Income Tax Return (2025 IL-1040)
Proof That You Mailed on Time
USPS Certified Mail with a return receipt gives you a tracking number and a signed confirmation of delivery. The current cost is $5.30 for the certified mail fee plus $4.40 for a hard-copy return receipt, on top of regular postage. An electronic return receipt is $2.82.6United States Postal Service. Notice 123 – Price List Under $10 for documented proof of timely filing is cheap insurance if you are mailing close to the deadline or owe a substantial balance.
E-Filing Instead
If the mailing process feels like more trouble than it’s worth, Illinois lets you file the IL-1040 electronically through MyTax Illinois at no cost. You can file without creating an account by selecting “File a 2025 IL-1040” under the Individuals tab. With a MyTax Illinois account you can also file prior-year returns going back to 2021.7Illinois Department of Revenue. File Form IL-1040, Individual Income Tax Return, on MyTax Illinois An e-filed return processes faster than paper, and you get confirmation of receipt without needing certified mail. The Department says e-filed refunds take about four weeks, while paper refunds run roughly four to eight weeks after filing.8Illinois Department of Revenue. Where’s My Refund?