Follow the steps to complete your CO DoR 104 online.

1. Click the ‘Get Form’ button to access the form and open it in the online editor.
2. Enter your personal information, starting with your last name, first name, and middle initial, along with your date of birth in MM/DD/YYYY format. Provide your Social Security Number (SSN) or Individual Taxpayer Identification Number (ITIN). If filing jointly, also input your partner's last name, first name, and date of birth, along with their SSN or ITIN.
3. Fill in your mailing address, including the city, state, and zip code. Additionally, enter your contact phone number for any follow-up communication.
4. Report your federal taxable income as shown on your federal income tax return (Form 1040, line 15). Make sure to round the amount to the nearest dollar.
5. Complete the additions to your federal taxable income, such as state addback, business interest expense deduction, and other relevant adjustments, as indicated in the form.
6. Calculate your total taxable income by applying the subtractions permitted on the form and ensuring compliance with the instructions for each section.
7. Enter any applicable nonrefundable credits you may have and calculate your net income tax based on the deductions taken.
8. Fill in the refund section if applicable, including your direct deposit information to receive any refunds electronically.
9. If necessary, complete the third-party designee section, allowing someone else to discuss your taxes with the Colorado Department of Revenue.
10. Lastly, provide signatures where required, ensuring both you and your partner (if applicable) sign and date the form. Review all entries for accuracy before submission.
11. Save your changes, and choose to download, print, or share the completed form as needed. Make sure to follow any specific mailing instructions provided.

Start filling out your CO DoR 104 online today to ensure your tax return is submitted on time.