Staying on top of tax deadlines is critical—especially for small business owners, S-Corp owners, real estate investors, and anyone making estimated tax payments. At Cardinal Tax, we want to help you stay organized so you avoid penalties, interest, and last‐minute stress. Here’s a clear breakdown of what to watch for in 2026, both at the federal level and in Maryland.
🏛 Federal Tax Deadlines (IRS)
Individual taxpayers (calendar‐year filers)
- April 15, 2026: Deadline to file your 2025 federal individual income tax return (Form 1040) and pay any tax owed.
- October 15, 2026: If you filed for an automatic extension (Form 4868) by April 15, you have until this date to file your 2025 return. Note: this is a filing extension—not an extension to pay.
Estimated tax payments (for taxpayers who don’t have sufficient withholding, e.g., self-employed, investors)
For the 2026 tax year:
- April 15, 2026 — 1st estimated payment due (income earned Jan 1–Mar 31).
- June 15, 2026 — 2nd estimated payment due (income earned Apr 1–May 31).
- September 15, 2026 — 3rd estimated payment due (income earned June 1–Aug 31).
- January 15, 2027 — 4th estimated payment due (income earned Sept 1–Dec 31, 2026).
Business / entity deadlines (calendar‐year entities unless otherwise noted)
- March 15, 2026: Deadline for calendar‐year partnerships (Form 1065) and S corporations (Form 1120-S).
- April 15, 2026: Deadline for calendar‐year C corporations (Form 1120) to file and pay.
- October 15, 2026: Extended deadline for individuals and C corporations if an extension was properly filed.
Important reminders:
- An extension to file is not an extension to pay. Taxes owed must be paid by the original due date (April 15 for individuals; earlier for some businesses) to avoid penalties and interest.
- Some deadlines may shift if they fall on weekends or holidays. Always confirm for your fiscal year end.
Maryland Tax Deadlines
Individual income tax (calendar-year filers for 2025):
- Filing due date: April 15, 2026.
- Automatic extension to file: October 15, 2026. Note: this is for filing only — taxes owed must still be paid by April 15, 2026.
- Estimated tax payments (calendar-year filers):
- Estimated tax payments (calendar‐year filers):
- April 15, 2026
- June 15, 2026
- September 15, 2026
- January 15, 2027
Pass-through entities (such as S corporations and partnerships) in Maryland for 2025 tax year:
- Filing due date: March 15, 2026.
- Extension to file: September 15, 2026.
Maryland C corporations for tax year 2025:
- Filing & payment due: April 15, 2026.
- Extension to file: November 16, 2026. Payment still due April 15, 2026.
Maryland Annual Report / Business Entity Maintenance:
- For Maryland LLCs, corporations, etc., the annual report & (in many cases) associated fee must be filed with the Maryland State Department of Assessments & Taxation (SDAT) by April 15 each year following the tax year (so for entities reflecting 2025 operations, report due April 15, 2026). Note: this is separate from the income tax return.
- Also, if eligible and participating in the MarylandSaves program waiver, election/claim must be made by December 31 of the prior year to qualify, so you should remind clients well ahead of December of the previous year.
✅ Quick Reference Table
| Deadline | Applies to | Date |
|---|---|---|
| Federal individual return (2025) | Most individuals | April 15, 2026 |
| Federal individual extension due date | Individuals who filed Form 4868 | October 15, 2026 |
| Federal estimated payments (2026 year) | Self‐employed / non‐wage income | April 15, June 15, Sept 15, Jan 15 2027 |
| Federal partnership / S‐Corp returns | Partnerships, S corporations | March 15, 2026 |
| Federal C corporation returns | C corporations | April 15, 2026 |
| Maryland individual return (tax year 2025) | Maryland resident individuals | April 15, 2026 |
| Maryland individual estimated payments | Non‐wage income in Maryland | April 15, June 15, Sept 15, Jan 15 2027 |
| Maryland pass‐through entity return | MD S corp / partnership | March 15, 2027 |
| Maryland C corporation return | MD C corporation | April 15, 2027 |
| Maryland Annual Report filing for LLCs/corps | All MD entities | April 15 each year (for first one after formation) |
Final Thoughts
At Cardinal Tax, our goal is to provide proactive tax planning, not just reactive compliance. By staying in front of these deadlines, we help our clients avoid unnecessary fees and focus on growth. Whether you’re a sole proprietor, an S‐Corp owner, or a real‐estate investor in Maryland, a little planning now goes a long way.
If you’d like help setting up reminders, estimating your 2026 tax liability, or understanding how these deadlines tie into your specific business structure (LLC, S corp, real estate investor, etc.), don’t hesitate to reach out. We’ll help you align your tax planning with your broader growth goals.