The majority of deadlines listed here are for Tax Year 2023. Some apply to upcoming Tax Years and some are IRS or Federal deadlines.
Prepare, eFile, Download
CO + IRS Tax Return
April 15, 2024
Tax Year 2023 Income Tax Return
Original Deadline to prepare and e-File a Colorado Income Tax Return. You have until October 15, 2024 to complete and e-File your Federal Income and Colorado State Income Tax Return.
eFileIT
April 15, 2024 (Deadline has passed. However, Colorado does offer an automatic tax extension.)
2023 Income Tax Extension
October 15, 2024
Tax Year 2023 Income Tax Return after the automatic April 15, 2024 Colorado Tax Extension
Last day to eFile a 2023 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
October 15, 2024 via mail-in Forms. Forms incl. Mailing Address are listed below.
Tax Year 2023 Income Tax Return after the automatic April 15, 2024 Colorado Tax Extension
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, 2024. (Optionally: the
eFileIT deadline is Oct. 15, 2024). Instructions on how to
only - without the IRS return -
prepare and file a Colorado State Income Tax Return on eFile.com.
Tax Amendment for All Tax Years
IRS Due Dates
IRS Tax Return, Extension, Amendment Deadlines
2023, 2024, etc.
Other State Tax Return, Extension, Amendment Deadlines
2023, 2024, etc.
IRS Federal Income Tax Return, Amendment, Extension Deadlines
April 15, 2025
2021 Colorado Income Tax Return Refund
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.
April 15, 2026
2022 Colorado Income Tax Return Refund
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.
April 15, 2027
2023 Colorado Income Tax Return Refund
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.
April 15, 2028
2024 Colorado Income Tax Return Refund
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.