April Tax Deadlines for US Small Business in 2026
All important April 2026 tax deadlines for sole proprietors, LLCs, S-Corps, and C-Corps. Don't miss a filing.
Tax deadlines are easy to miss — and expensive. Here's every major federal tax deadline in April 2026 that affects US small businesses.
Quick overview
- April 15 — Individual tax return (Form 1040) due
- April 15 — C-Corp tax return (Form 1120) due
- April 15 — Q1 estimated tax payment
- April 15 — Last day to contribute to IRA/Roth for prior year
- April 15 — HSA contribution deadline for prior year
- April 30 — Form 941 Q1 deadline
Detail on each deadline
April 15: Individual tax return (Form 1040) due
Missing this deadline usually triggers a penalty of 5% per month (capped at 25%) plus interest. File even if you can't pay — the failure-to-file penalty is 10x the failure-to-pay penalty.
April 15: C-Corp tax return (Form 1120) due
Missing this deadline usually triggers a penalty of 5% per month (capped at 25%) plus interest. File even if you can't pay — the failure-to-file penalty is 10x the failure-to-pay penalty.
April 15: Q1 estimated tax payment
Missing this deadline usually triggers a penalty of 5% per month (capped at 25%) plus interest. File even if you can't pay — the failure-to-file penalty is 10x the failure-to-pay penalty.
April 15: Last day to contribute to IRA/Roth for prior year
Missing this deadline usually triggers a penalty of 5% per month (capped at 25%) plus interest. File even if you can't pay — the failure-to-file penalty is 10x the failure-to-pay penalty.
April 15: HSA contribution deadline for prior year
Missing this deadline usually triggers a penalty of 5% per month (capped at 25%) plus interest. File even if you can't pay — the failure-to-file penalty is 10x the failure-to-pay penalty.
April 30: Form 941 Q1 deadline
Missing this deadline usually triggers a penalty of 5% per month (capped at 25%) plus interest. File even if you can't pay — the failure-to-file penalty is 10x the failure-to-pay penalty.
Not sure which deadlines apply to you?
It depends on your entity type:
- Sole proprietor / single-member LLC: file Schedule C with Form 1040 by April 15
- Multi-member LLC / partnership: Form 1065 by March 15
- S-Corp: Form 1120-S by March 15
- C-Corp: Form 1120 by April 15 (or 15th of 4th month after fiscal year-end)
- Employer: Form 941 quarterly, W-2/1099 annually
How TinSuite helps you stay on top
- Deadline calendar built into your dashboard
- Email and in-app reminders 7 and 1 day before each deadline
- Pre-filled forms generated from your books — just review and file
- Multi-state aware — adds state deadlines based on your nexus