The majority of deadlines listed here are for Tax Year 2024. Some apply to upcoming Tax Years and some are IRS or Federal deadlines.
Deadline:Prepare, eFile, Download
CO + IRS Tax Return
Deadline:April 15, 2025
Type:Tax Year 2024 Income Tax Return
Description:Original Deadline to prepare and e-File a Colorado Income Tax Return. You have until October 15, 2025 to complete and e-File your Federal Income and Colorado State Income Tax Return.
eFileIT
Deadline:April 15, 2025 (Deadline has passed. However, Colorado does offer an automatic tax extension.)
Type:2024 Income Tax Extension
Deadline:October 15, 2025
Type:Tax Year 2024 Income Tax Return after the automatic April 15, 2025 Colorado Tax Extension
Description:Last day to eFile a 2024 Colorado State Income Tax Return for Tax Extension Filers and late eFilers. You can
only eFile (to file by paper see below) Colorado Income Tax Return together with an IRS Tax Return.
eFileIT
Deadline:October 15, 2025 via mail-in Forms. Forms incl. Mailing Address are listed below.
Type:Tax Year 2024 Income Tax Return after the automatic April 15, 2025 Colorado Tax Extension
Description:Deadline for taxpayers who got an automatic CO Tax Extension to file their Colorado Income Tax Return by mail-in Forms - the Forms incl. mailing addresses are listed below - is October 15, 2025. (Optionally: the
eFileIT deadline is Oct. 15, 2025). Instructions on how to
only - without the IRS return -
prepare and file a Colorado State Income Tax Return on eFile.com.
Type:Tax Amendment for All Tax Years
Deadline:IRS Due Dates
Type:IRS Tax Return, Extension, Amendment Deadlines
Deadline:2024, 2025, etc.
Type:IRS Federal Income Tax Return, Amendment, Extension Deadlines
Deadline:April 15, 2025
Type:2021 Colorado Income Tax Return Refund
Description:The last day to file and claim your 2021 Colorado Income Tax Return. This deadline does not apply if you owe Income Taxes.After that date your 2021 tax refund will expire.
Details.
Deadline:April 15, 2026
Type:2022 Colorado Income Tax Return Refund
Description:The last day to file and claim your 2022 Colorado Income Tax Return. This deadline does not apply if you owe Income Taxes. After that date your 2022 tax refund will expire.
Details.
Deadline:April 15, 2027
Type:2023 Colorado Income Tax Return Refund
Description:The last day to file and claim your 2023 Colorado Income Tax Return. This deadline does not apply if you owe Income Taxes. After that date your 2023 tax refund will expire.
Details.
Deadline:April 15, 2028
Type:2024 Colorado Income Tax Return Refund
Description:The last day to file and claim your 2024 Colorado Income Tax Return. This deadline does not apply if you owe Income Taxes. After that date your 2024 tax refund will expire.
Details.