Which return is yours?
| Entity | Federal form | Usual due date |
|---|---|---|
| Sole proprietor / single-member LLC | Schedule C with Form 1040 | April 15 |
| Partnership / multi-member LLC | Form 1065 + K-1s | March 15 |
| S-corporation | Form 1120-S + K-1s | March 15 |
| C-corporation | Form 1120 | April 15 |
Colorado has matching state returns for pass-through entities and corporations. Denver adds its own sales and use tax and occupational privilege tax filings on a monthly or quarterly schedule, depending on your volume.
What makes a return hold up
- Books that tie to bank statements before the return starts
- Owner pay and distributions recorded correctly (especially for S-corps)
- Depreciation schedules carried forward accurately year to year
- K-1s that match what each owner reports on their personal return
- State apportionment if you sell outside Colorado
The S-corp question
Plenty of Denver owners elect S-corp status to save self-employment tax, then skip the reasonable salary that makes the election work. If the IRS looks, that's the first thing it checks. A business tax preparer should set salary based on your role and industry, then run payroll to match.
Plan, don't just file
The best business return is the one with no surprises in it. Quarterly check-ins let you adjust estimates, time big purchases and decide on retirement contributions before the year ends, not after.
Common questions
When are business tax returns due?
Calendar-year S-corporation and partnership returns are generally due March 15, and C-corporation returns April 15. Dates move to the next business day when they land on a weekend or holiday.
What's the penalty for filing a partnership or S-corp return late?
The IRS charges a per-partner or per-shareholder penalty for each month the return is late, so even small entities can rack up penalties fast.
Do I need a separate Colorado business return?
Most pass-through entities file a Colorado partnership or S-corporation return, and C-corporations file a Colorado corporate return, in addition to the federal one.