How to File Your Colorado Tax Return for 2018

In 2018, more than 2.7 million Colorado taxpayers filed their state income tax returns, yet thousands lost out on refunds simply because of missed deadlines or minor filing errors. For many, these mistakes meant waiting months for money that could have been in their account in just weeks. Filing correctly the first time is not only about compliance—it’s about protecting your finances and avoiding unnecessary stress.

This guide will walk you through how to file your Colorado tax return for the 2018 tax year. Whether you are an individual taxpayer, a sole proprietor, or a small business owner, you will learn which forms you need, the deadlines you must meet, and the most efficient ways to submit your return. The process is based entirely on official Colorado Department of Revenue guidelines, so you can file with confidence knowing you have the correct information.

Filing early, filing electronically, and claiming every credit you qualify for—such as the child tax credit or other deductions—can help you maximize your refund and avoid costly mistakes. Waiting until the last minute increases the risk of penalties, interest charges, and delayed refunds. This guide will meet the state’s legal requirements and position you to keep more of your hard-earned money.

Who Needs to File a Colorado Tax Return for 2018

Filing requirements in Colorado are closely tied to your federal income tax obligations. If you were required to file a federal return for the 2018 tax year, you must also file a Colorado return. This applies whether you are a full-year, part-year, or non-resident with income from Colorado sources. Even if you do not owe state taxes, filing ensures you avoid processing delays, resolve potential discrepancies, and receive any refund you may be entitled to.

Full-year residents must file a federal return if required, regardless of whether Colorado tax is owed. Part-year residents must file if they earned taxable income while living in Colorado in 2018. Non-residents must file if they earned income from Colorado sources during that year. The Colorado Department of Revenue uses your federal taxable income as the starting point for calculating your state income tax, so completing your federal return first is essential.

It is essential to be aware that the Department of Revenue may file a return on your behalf using limited information if you do not submit one yourself. This process will not consider deductions, credits, or adjustments you might qualify for, which could mean losing a refund or paying more than necessary. By filing your complete return, you maintain control over your tax account, ensure accuracy, and protect your financial interests.

Key Deadlines and What They Mean for Taxpayers

Meeting the filing deadlines for the 2018 tax year is critical for every Colorado taxpayer. The standard due date for individual income tax returns was April 15, 2019. Missing this date during tax season could result in a penalty and added interest, even if you qualify for a refund. Filing on time avoids unnecessary costs and ensures you receive your refund promptly. Electronic returns are processed in about two to three weeks, while paper returns take six to eight weeks.

Automatic Extension

• Colorado provided an automatic six-month extension to file, moving the deadline to October 15, 2019, for paperwork only.
• Any taxes owed were still due by April 15, and you needed to pay at least 90% of your balance by that date to avoid penalties.
• For taxpayers living or traveling abroad on April 15, a special June 17, 2019, deadline applied for filing and payment without penalty.
• Be aware that missing these deadlines, even briefly, can trigger additional costs.

Penalties and Interest

• Late filing penalty: 5% of unpaid tax for the first month, plus 0.5% for each additional month, up to a maximum of 12%.
• Interest accrues on unpaid balances until paid in full. Suppose you cannot pay in full, file on time, and contact the Colorado Department of Revenue to set up a payment plan. This is far less costly than ignoring the due dates entirely.

Forms You Need for Filing

Colorado requires specific forms for the 2018 tax year, and using the correct ones is essential to avoid processing delays. All forms can be accessed through the Colorado Department of Revenue website or by logging in to Revenue Online.

Main Form

• DR 0104 – Colorado Individual Income Tax Return: Required for all residents, part-year residents, and non-residents with Colorado income. Use this to report your state income tax and claim any applicable adjustments or credits.

Common Schedules and Supporting Forms

• DR 0104AD – Subtractions from Income: Needed if you are claiming subtractions such as U.S. government interest or pension income.
• DR 0104CR – Individual Income Tax Credit Schedule: Use to claim credits like the child tax credit or other state-specific tax credit programs.
• DR 0104PN – Part-Year/Nonresident Computation Form: Calculates tax on Colorado-sourced income for those who lived in the state for only part of the year.
• DR 0104US – Consumer Use Tax Reporting Schedule: Required if you owe use tax on out-of-state purchases.

Payment and Extension Forms

• DR 0900 – Payment Voucher: Include when mailing a payment separately from your tax returns.
• DR 0158-I – Extension Payment Form: Use if you request a filing extension and owe payment.

Amendments

• DR 0104X – Amended Individual Income Tax Return: File this if you need to correct a previously submitted return.

Mailing Addresses

If including a payment:
Colorado Department of Revenue  

Denver, CO 80261-0006

If no payment is due:
Colorado Department of Revenue  

Denver, CO 80261-0005

Filing online through Revenue Online allows you to complete and submit your forms without mailing them, access your account immediately, and upload any supporting documents electronically.

Step-by-Step Filing Process

Filing your 2018 Colorado individual income tax return is more straightforward when you follow each step in order. This process is based on official state guidance and is designed to help you avoid costly mistakes.

Step 1: Gather Your Documents

Before starting, make sure you have everything you need:

• Income documents: W-2s, 1099s, and Schedule K-1s.
• Your federal income tax return (Form 1040).
• Records of tax credit eligibility, such as the child tax credit or other deductions.
• Proof of any estimated tax payments made during 2018.
• Additional information for subtractions or adjustments (e.g., charitable donations, pension income).

Being fully prepared helps you complete your filing without delays and reduces the chance of missing out on tax benefits.

Step 2: Complete Your Federal Return First

Colorado begins its income tax calculation with your federal taxable income. You cannot accurately complete your DR 0104 without finishing your federal return. If you skip this step, your state filing will be incomplete and could result in processing issues or incorrect payments.

Step 3: Fill Out Form DR 0104

• Enter personal details: name, Social Security number, address, and filing status.
• Indicate your residency status (full-year, part-year, or non-resident).
• Line 1: Enter your federal taxable income.
• Line 2: Add back certain deductions if required.
• Line 5: Subtract qualifying amounts (complete DR 0104AD if needed).

Step 4: Calculate Your Colorado Individual Income Tax

• Full-year residents: Apply the 4.63% tax rate to your Colorado taxable income.
• Part-year/non-residents: Complete DR 0104PN to prorate your taxes.
• Apply applicable credits using DR 0104CR, including any child or state-specific tax credit.

Step 5: Report Payments and Withholding

On the DR 0104:

• Enter Colorado income tax withheld from W-2s/1099s (attach copies).
• Include prior-year credit carryovers and estimated payments.
• Calculate your payment due, including any fees or penalties if you owe taxes.

Step 6: Review for Common Errors

Before submitting:

• Make sure your math is correct.
• Confirm all forms are signed and dated.
• Verify your Social Security number.
• Be aware that missing or incomplete forms can delay your refund and create additional work to manage later.

Many people file online through Revenue Online because it manages form calculations, helps avoid errors, and allows faster processing. While paper filing is available, it is slower, less efficient, and can result in delays if forms are incomplete.

How to File—Online vs. Mail

Colorado offers two main ways to file your 2018 individual income tax return: electronically through Revenue Online or by mailing paper forms. Each method has its advantages, but most taxpayers benefit from filing online.

Filing Online Through Revenue Online

• Fast and efficient: Returns filed online are usually processed in two to three weeks.
• Free access: You can use Revenue Online at no cost to complete and submit your return.
• Convenient features:
  
  • Upload supporting documents directly from your computer.
  • Access your tax account history anytime.
  • Receive immediate confirmation when your filing is submitted.
• Error reduction: The system performs basic checks, reducing the risk of calculation mistakes.

How to Access: Go to Colorado.gov/RevenueOnline and choose the “File a Return” option. No login is required for filing, but creating an account gives you more control over managing your information.

Filing by Mail

If you prefer or need to file by mail, follow these steps:

1. Print and complete all necessary forms for your 2018 return.
2. Double-check that your Social Security number, address, and amounts are correct.
3. Use the correct mailing address:
4. Send using first-class U.S. mail for faster delivery.

Mailing can take significantly longer. If deadlines are approaching, filing online is safer to ensure your return is received on time. If you have questions about either method, contact the Colorado Department of Revenue for assistance.

Payment Options and Setting Up Payment Plans

If you owe Colorado state income tax for the 2018 tax year, the Department of Revenue offers multiple payment options to help you manage your balance. Choosing the correct method can save time, reduce fees, and keep your account in good standing.

Online Payment Options

• Revenue Online
  
  • Pay directly through the state’s secure portal.
  • Accepted methods: credit card, debit card, e-check, or electronic funds transfer (EFT).
  • Some payment types may have small processing fees.
  • You can also schedule future payments or manage your account online.

Traditional Payment Methods

• Check or Money Order
  
  • Make payable to: Colorado Department of Revenue.
  • Write your Social Security number, tax year, and “2018 DR 0104” on the memo line.
  • Include the DR 0900 payment voucher if mailing separately.

Payment Plans

If you cannot pay your total balance at once:

• Wait for the Department of Revenue to send a billing notice.
• Log in to Revenue Online to request a payment plan or contact their services line for assistance.
• Plans allow you to pay in monthly installments, helping you avoid additional penalties while you pay off your balance.

Paying as much as possible by the April deadline will reduce interest and fees, even if you enter into a payment plan later. Proactively managing your account keeps your debt from growing unnecessarily.

How to Track Your Refund or Balance Due

Once your 2018 Colorado individual income tax return is filed, you can track your refund or check any balance due through Revenue Online. This secure portal gives you access to your tax account 24/7, allowing you to view the status of your return, see payment history, and manage your account without having to call or mail forms.

Checking Your Refund Status

• Log in to Revenue Online or use the “Where’s My Refund?” tool without an account.
• Enter your Social Security number, refund amount, and tax year to check the progress.
• Refunds for electronic filings are typically issued in two to three weeks, while paper returns may take six to eight weeks.
• If the Department of Revenue sends you a note or letter requesting additional information, respond quickly to avoid delays. These letters often concern identity verification or missing documentation.

Viewing and Managing a Balance Due

• Revenue Online also lets you review your account to see if you still owe taxes for the 2018 tax year.
• You can manage payments, set up a plan, or immediately pay directly from your computer.
• You can contact the Colorado Department of Revenue by phone for assistance with your account.

Tip: Always check the subject line of any official note or letter you receive. This helps you identify whether it concerns a refund delay, missing forms, or an outstanding balance. Ignoring correspondence can result in penalties or additional interest charges.

Requesting an Extension

If you cannot file your 2018 Colorado tax return by the standard deadline, the state offers an automatic six-month extension to submit your paperwork. This moves the due date from April 15, 2019, to October 15, 2019. However, it is essential to know that this extension applies only to filing your tax returns—not to making your payment.

When and How to Request an Extension

• If you are not making a payment, you do not need to file a special form to get the automatic extension.
• If you owe taxes and need to send money with your extension, use Form DR 0158-I to submit your payment by April 15.
• You can mail this form with a check or pay through Revenue Online.

Why Timely Payment Still Matters

Even with an extension to file, you must pay at least 90% of your total tax owed by April 15 to avoid late-payment penalties and interest. If you underpay, the remaining balance will accrue charges until it is settled.

Final Filing Checklist

Before you send your 2018 Colorado individual income tax return, ensure your filing is accurate, complete, and includes all required documents. Skipping even one step in the process can delay your refund or lead to notices from the Department of Revenue.

Documents to Include

• Completed forms for your return (DR 0104 and any supporting schedules).
• W-2s and 1099s showing Colorado tax withheld.
• Provide proof of any deductions or credits claimed, including the child tax credit or other subtractions.
• Additional information for adjustments, such as pension income or charitable donations, is required.

Accuracy Checks

• Double-check all math and ensure totals match your federal return.
• Confirm your Social Security number and address are correct.
• Be aware of residency status entries—errors here can cause processing issues.
• Make sure your payment amount is correct if you owe taxes.

Submission Steps

• Sign and date all forms.
• If mailing, use the correct address based on whether you are including a payment.
• Keep copies of everything for at least four years in case of an audit.

Taking a few extra minutes to review your return can save weeks of delay and prevent costly mistakes.

Frequently Asked Questions

How do I claim the child tax credit on my Colorado tax return for 2018?

To claim the child tax credit, complete your federal return first, since Colorado’s credit amount is directly tied to your federal calculation. Once the federal figure is established, transfer it to the DR 0104CR form. A person claiming this credit must meet all IRS eligibility rules, which include having a qualifying child, meeting income limits, and filing the correct status. 

Can I pay my Colorado taxes for 2018 using a money order?

You can pay with a money order payable to “Colorado Department of Revenue.” Always write your Social Security number, the tax year, and “2018 DR 0104” in the memo line to ensure it is applied correctly. Include the DR 0900 payment voucher if sending separately from your return. The IRS recognizes this payment type as a secure method for taxpayers who prefer not to use electronic transactions. 

What should I do if the Department of Revenue requests additional information for my return?

If you receive a letter requesting additional information, respond quickly to prevent delays in processing your refund or finalizing your balance. A person should carefully read the instructions and submit the requested documentation in the specified format. Sometimes, the IRS and Colorado Department of Revenue coordinate data checks, so providing the correct information ensures both agencies have matching records. 

Can one person file both federal and Colorado state returns at the same time?

Yes, if you use approved tax software or a professional preparer who offers combined filing services. This means the IRS will receive your federal return while Colorado receives your state return in the same electronic transmission. For a person looking to save time, this approach is convenient, reduces the chance of errors, and allows you to receive both refunds faster.

What happens if I don’t respond to the IRS or Colorado about my 2018 taxes?

Failing to respond to the IRS or Colorado Department of Revenue could lead to serious consequences, including delayed refunds, loss of credits, or added penalties and interest. A person who ignores official letters or notices risks additional tax assessments that may be difficult to dispute later. Both agencies can change your return without input if you do not provide the requested documentation.