Mail your Colorado state tax return to the Colorado Department of Revenue

The Colorado Department of Revenue processes all state income tax returns. You send your return to a specific mailing address depending on whether you owe money, expect a refund, or are filing an amended return. The address you use matters because it routes your return to the correct processing center, which speeds up handling and reduces errors.

Do not mail your return to a local tax office or county assessor. The state operates a single processing center for all returns, and using the wrong address delays your refund or payment processing by weeks.

Key Takeaways

  • Mail returns that include a payment to the Department of Revenue at 1375 Sherman Street, Denver, CO 80261.
  • Mail returns without payment (refunds only) to the same address: 1375 Sherman Street, Denver, CO 80261.
  • Amended returns go to the same mailing address but should include a note on the envelope stating "Amended Return" so staff route it correctly.
  • The Colorado Department of Revenue does not accept returns at county offices, local tax agencies, or any other state building.
  • If you file electronically through approved software or a tax professional, you do not use a mailing address at all.

Standard mailing address for all paper returns

Whether you are sending a return with a check, a return requesting a refund, or a return showing zero tax owed, use this address:

Colorado Department of Revenue 1375 Sherman Street Denver, CO 80261

This is the only mailing address the state accepts for individual income tax returns. Returns sent to any other state office or county location will be forwarded to this address, which adds processing time.

Include your name, address, and Social Security number on the return itself. Write your name and Social Security number on any check you enclose. Do not send cash.

How to handle amended returns

An amended return corrects errors on a return you already filed. Mail it to the same address as a regular return, but write "Amended Return" clearly on the front of the envelope. This alerts staff to match it with your original return rather than treating it as a duplicate filing.

Include a copy of the original return if you have one, or at minimum the tax year and your Social Security number so the department can locate your file. Processing an amended return typically takes longer than a new return because staff must review both versions.

Do not file an amended return if you are only correcting a math error. The Colorado Department of Revenue catches and corrects math errors automatically during processing, and you will see the correction on your notice of assessment.

Timing and what to expect after mailing

Mail your return early enough to arrive before the filing important date. The important date is usually April 15, but the state counts the postmark date, not the arrival date. A return postmarked by April 15 is considered on time even if it arrives in Denver weeks later.

After the department receives your return, processing typically takes 4 to 8 weeks if you are expecting a refund and the return has no errors. Returns with payments or amendments may take longer. You can check the status of your return on the Colorado Department of Revenue website once processing begins.

If you are owed a refund, the state issues it by check or direct deposit depending on how you filed. Direct deposit refunds arrive faster than checks, usually within 2 to 3 weeks of approval.

Electronic filing as an alternative to mailing

You can file your Colorado return electronically through approved tax software, a tax professional, or the IRS Free File program if your income is below the threshold. Electronic returns are processed faster than paper returns and reduce the chance of errors.

If you file electronically, you do not mail anything to the Colorado Department of Revenue. The software or tax professional transmits your return directly to the state system. You will receive a confirmation number showing your return was received.

Electronic filing is especially useful if you are sending a payment, because you can pay online at the same time you file. The state accepts credit cards, debit cards, and electronic bank transfers for online payments.

What not to do when mailing your return

Do not mail your return to the IRS address. The IRS processes federal returns only. Colorado state returns must go to the Colorado Department of Revenue address in Denver.

Do not mail your return to a county assessor, county clerk, or local tax office. These offices do not process state income tax returns and will have to forward your return to Denver, adding weeks to processing time.

Do not send your return by certified mail or require a signature unless you are sending a large payment and want proof of delivery. Regular first-class mail is sufficient and faster because it does not require signature confirmation.

Do not include documents like W-2s, 1099s, or receipts with your mailed return unless the Colorado Department of Revenue specifically requests them. Keep these documents for your records. Sending extra papers slows down processing.

If you need to contact the department about your return

The Colorado Department of Revenue has a phone line for tax questions and return status. You can reach them during business hours to ask about a return you mailed or to clarify filing requirements.

If you are unsure whether your return arrived, wait at least two weeks after mailing before calling. The department needs time to log incoming mail and enter returns into the system. Calling too early means staff cannot locate your return yet.

Have your Social Security number and tax year ready when you call. This helps staff find your file quickly.

Frequently Asked Questions

Can I mail my Colorado return to a different address if I live out of state?

No. All Colorado state returns go to 1375 Sherman Street, Denver, CO 80261, regardless of where you live. The state processes all returns at this single location. Living out of state does not change the mailing address.

What if I mail my return but forget to include my Social Security number?

The department will contact you by mail asking for your Social Security number so they can process your return. This delays processing by several weeks. Always include your Social Security number on the return and on any check you send.

Do I need to mail my return if I file electronically?

No. Electronic returns go directly to the state system through tax software or a tax professional. You do not mail anything. Keep a copy of your electronic filing confirmation for your records.

How long does it take for a mailed return to be processed?

Processing typically takes 4 to 8 weeks for returns without errors. Returns with amendments or that require staff review may take longer. You can check your return status on the Colorado Department of Revenue website once processing begins.

What if I owe money — do I still mail to the same address?

Yes. Mail returns with payment to 1375 Sherman Street, Denver, CO 80261. Write your Social Security number on your check and include it with your return. The department will process your payment and return together.