LLC Tax Deadlines 2026: Complete Calendar for Business Owners
Miss a tax deadline, pay for months. The IRS doesn't care about good intentions—only timely filings. This calendar covers every deadline your LLC needs to hit in 2026.
Quick Reference: 2026 LLC Tax Calendar
Mar 15
Partnership Form 1065
S-Corp Form 1120-S
S-Corp Form 1120-S
Apr 15
Q1 Estimated Tax
Sole Prop Schedule C
Sole Prop Schedule C
Jun 15
Q2 Estimated Tax
Sep 15
Q3 Estimated Tax
Extended Partnership/S-Corp
Extended Partnership/S-Corp
Oct 15
Extended Personal Return
Extended C-Corp
Extended C-Corp
Jan 15, 2027
Q4 Estimated Tax
Deadlines by LLC Tax Classification
Your filing deadlines depend on how your LLC is taxed:
| Tax Classification | Tax Form | Deadline | Extension Deadline |
|---|---|---|---|
| Sole Proprietorship (single-member) | Schedule C (with 1040) | April 15 | October 15 |
| Partnership (multi-member) | Form 1065 | March 15 | September 15 |
| S-Corp Election | Form 1120-S | March 15 | September 15 |
| C-Corp Election | Form 1120 | April 15 | October 15 |
Quarterly Estimated Tax Deadlines
All LLC members (regardless of classification) must pay estimated taxes quarterly if you expect to owe $1,000+ at year-end:
| Quarter | Period Covered | Deadline |
|---|---|---|
| Q1 | Jan 1 – Mar 31 | April 15, 2026 |
| Q2 | Apr 1 – May 31 | June 15, 2026 |
| Q3 | Jun 1 – Aug 31 | September 15, 2026 |
| Q4 | Sep 1 – Dec 31 | January 15, 2027 |
Common mistake: Paying all estimated taxes on April 15. Each quarter has its own deadline. Missing Q2, Q3, or Q4 triggers penalties even if you eventually pay in full.
Penalty Calculations
Late Filing Penalty
- 5% of unpaid tax per month (max 25%)
- Additional 0.5% per month for late payment
- Interest compounds daily on unpaid balance
Estimated Tax Underpayment Penalty
- Roughly 8% annually on shortfall (2026 rate)
- Calculated quarterly, not annually
- Safe harbor: Pay 100% of prior year tax (110% if AGI > $150K)
Example Penalty Scenario
LLC owes $20,000 in taxes, files 2 months late:
- Late filing: 5% × 2 months = $2,000
- Late payment: 0.5% × 2 months = $200
- Interest (approx): $200
- Total penalty: ~$2,400
State-Specific Deadlines
State deadlines vary significantly. Common patterns:
- California: $800 minimum annual tax due by 4/15 (no exceptions)
- New York: Publication requirement within 120 days of formation
- Delaware: Annual franchise tax due June 1
- Texas: Franchise tax due May 15 (no income tax)
- Florida: No state income tax, but annual report due May 1
Extension Strategy
Filing an extension is free and automatic—but it doesn't extend payment deadlines.
- File Form 7004 (business) or Form 4868 (personal) by original deadline
- Pay estimated taxes by original deadline (at least 90% of expected liability)
- Use the extra 6 months to gather documentation, not procrastinate
Extensions are strategic tools, not escape hatches. Use them when you need time for accurate filing—not when you're avoiding taxes.
S-Corp Election Deadline
If you want S-Corp tax treatment for 2026:
- Existing LLC: File Form 2553 by March 16, 2026 (75-day rule)
- New LLC: File within 75 days of formation date
- Late election: Requires IRS approval via revenue procedure—not guaranteed