January 13, 2025
2025 tax deadlines for Colorado small businesses
The dates that actually matter this year — federal and Colorado, filing and estimates — in one place, so nothing sneaks up on you.
Half of staying out of penalty trouble is just knowing the dates. Here are the deadlines that matter for a Colorado small business this year, in plain order. Bookmark it — and remember that when a date lands on a weekend or holiday, it generally rolls to the next business day.
Filing deadlines
- March 15 — S-corporation (1120-S) and partnership (1065) returns are due, or file an extension. This is the one business owners forget, because it comes a month before the “tax day” everyone knows.
- April 15 — personal returns (1040) and C-corporation (1120) returns are due, along with your Colorado individual return. File an extension here if you need one.
- September 15 — extended S-corp and partnership returns are due.
- October 15 — extended personal returns are due.
An extension gives you more time to file, not more time to pay. If you expect to owe, you still need to pay by the original deadline to avoid interest.
Quarterly estimated taxes
If you pay estimates — and most profitable owners should — the four dates are:
- April 15 (Q1)
- June 15 (Q2)
- September 15 (Q3)
- January 15 of next year (Q4)
These apply to both your federal and Colorado estimates. Our quarterly-estimates guide covers the safe-harbor math that makes them penalty-proof.
Don’t forget the recurring ones
Beyond the big annual dates, a business with employees or sales has rhythms of its own: payroll tax deposits and quarterly 941s, sales-tax returns (generally due the 20th of the following month), and local filings like Denver’s OPT. Those are easy to lose track of precisely because they repeat.
The cleanest way to never miss a date is to not rely on remembering them. If you would rather have someone simply keep you ahead of all of it, that is a large part of what we do.
This is general information for Colorado business owners, not individual tax advice, and dates shift for weekends and holidays. Confirm the current deadlines with the IRS and Colorado Department of Revenue, or with a CPA.