Tax season isn’t just once a year, it’s all year long for small business owners. A late Business tax return filing can cost you more than money. Remain compliant and safeguard your bottom line by putting these vital tax dates in your calendar. But missing them? That can result in costly fines, penalties, or even IRS notices, all of which are completely avoidable with a little planning. Stay organized and avoid errors in tax preparation by getting ahead of these key deadlines.
Below is a handy breakdown of key U.S. tax deadlines every small business owner should know (including LLCs, sole props, S Corps, and partnerships).
1. January 31 – 1099-NEC and W-2 Filing Deadline
If you paid independent contractors ($600 or more) or have employees:
- File Form 1099-NEC with the IRS and provide copies to contractors.
- File W-2s for employees and send them their copies as well.
Penalties for late filing: Up to $310 per form!
Various software for e-filing:
- IRS IRIS Taxpayer Portal (Free)
- Tax1099
- efile4Biz
2. March 15 – S Corporation & Partnership Tax Returns (Form 1120S / 1065)
If your business is an S corporation or partnership, your tax return is due March 15, not April 15.
- Use Form 1120S for S corps
- Use Form 1065 for partnerships
- Also distribute Schedule K-1 to all shareholders/partners
Penalties for Late Filing:
- Form 1065: The IRS may impose a penalty of $220 per partner per month for up to 12 months for late filing.
- Form 1120-S: Similar penalties apply for late tax filing, emphasizing the importance of meeting deadlines.
Missing this deadline? File Form 7004 for an automatic 6-month extension.
Various software for e-filing:
- Drake
- TurboTax
- TaxAct
- Lacerte
3. April 15 – Individual & Sole Proprietor Tax Returns (Form 1040 + Schedule C)
If you’re a sole proprietor or single-member LLC, this is your big one.
- File your Form 1040 with Schedule C – Reports profit or loss from business activities.
- Include Schedule SE if you’re self-employed – Calculates self-employment tax if your net earnings exceed $400.
Need more time? File Form 4868 for a 6-month extension but still pay any tax owed by April 15 to avoid interest and penalties.
4. April 15 – First Estimated Tax Payment (Form 1040-ES, Q1)
If you’re self-employed or don’t have taxes withheld (like most small business owners), you likely need to pay quarterly estimated taxes.
2025 Estimated Tax Due Dates:
- Q1: April 15
- Q2: June 16 (because June 15 is a Sunday)
- Q3: September 15
- Q4: January 15 (of the following year)
Miss these? You may face underpayment penalties, even if you pay in full by year-end.
5. September 15 – Extended Deadline for S Corps & Partnerships
If you filed an extension back in March, this is your new deadline for:
- Form 1120S (S corp)
- Form 1065 (partnership)
- Distributing updated Schedule K-1s
6. October 15 – Extended Individual Tax Return Deadline
If you filed Form 4868 in April, this is your new due date to submit:
- Form 1040
- Schedule C
- State returns (if applicable)
This is a filing extension, not a payment extension. Interest continues to accrue after April 15.
Sales Tax, Payroll Tax & Other State-Specific Deadlines
These vary based on your state and business structure but may include:
- Monthly or quarterly sales tax filings
- Payroll tax deposits (Form 941, state withholding)
- State franchise or excise taxes
How to Save Yourself from Penalties and Stay on Track
- Use a tax calendar tool or set calendar alerts
- Work with a tax pro to file extensions and plan ahead
- Set aside cash for estimated taxes monthly, not quarterly
- Work with a tax pro or bookkeeper
- Stay organized, clean books save time & avoid tax hassle
- Don’t wait until the last minute
- Choose the right filing software
Conclusion
Keeping on top of your small business tax deadlines isn’t merely a matter of avoiding penalties, it’s about maintaining control of your finances throughout the entire year. When there are so many forms, schedules, and changing due dates, it’s tempting to become swamped. That’s why remaining organized, getting ahead, and working with specialists who know the nuances of business compliance is so vital.
If you’re unsure about any deadlines or need help navigating tax filings, consulting with a trusted bookkeeping and tax support provider can make all the difference. Alpha Accounting specializes in outsourced tax preparation and bookkeeping for accounting firms and CPAs, helping you or your clients stay compliant, accurate, and stress-free throughout the year.