Over 142 million tax returns landed on the IRS’s desk this April. That’s a lot of paperwork and probably a big sigh of relief for most people.
But for small business owners, that’s not the end of the story.
Sure, April 15 is a major milestone, but it’s not the finish line (not even close). There are still important IRS deadlines ahead, and missing them can mean penalties, interest, and the kind of attention from the IRS that your business is better off without.
In this blog, we’ll discuss the key post-April tax deadlines that small business owners need to stay on top of.
June 16, 2025 – second-quarter estimated tax payment due
With the first quarter of 2025 behind us, it’s time to turn your attention to your second-quarter estimated tax payment that’s due June 16. If you haven’t already, it’s also a good time to review your estimated income for the year and adjust your payments if necessary so you are prepared for the next quarterly payments and consequent IRS deadlines.
Also read: How to prep your small business for tax season: 6 strategies for smooth filings
September 15, 2025 – third-quarter estimated tax payment due
September 15 marks the deadline for your third-quarter estimated tax payment for 2025.
This is one of the IRS quarterly tax deadlines that aren’t just for individual filers; it also marks the deadline for extended partnership and S-corporation returns. If you’re a business owner who filed for an extension earlier in the year, this is the time to file your return if you haven’t already. Missing this deadline can result in penalties.
October 15, 2025 – extended tax return deadline
If you are an individual filer who filed an extension for your tax return earlier this year, mark October 15th as your final deadline. You’ll need to submit your completed 2024 tax return by this date. Missing it can result in significant penalties and interest, so it’s important to stay on track.
The key here is to plan ahead and gather all your information well before the IRS deadlines so you’re not rushing at the last minute. It also reduces the risk of errors that could lead to delays or penalties.
January 15, 2026 – fourth-quarter estimated tax payment due
The final estimated tax payment for 2025 is due on January 15, 2026. Sure, it’s still months away, but if you don’t plan ahead, it can sneak up fast, and missing it is the last thing you want. If you’ve been making your estimated payments throughout the year, this is your last opportunity to settle up before the next tax cycle begins. And if you’ve overpaid, you could get a refund or apply the extra toward next year’s payments.
Other important dates to remember
While small business tax due dates are at the forefront, here are a few additional IRS deadlines to keep in mind:
- Required minimum distributions (RMDs): If you turned 73 in 2024, you’ll need to take your first RMD by April 1, 2025. You’ll also need to take your RMD for 2025 by December 31, 2025. If you miss these dates, you could face significant penalties.
- Form W-2 and 1099-NEC filing deadline: If you have employees or hire independent contractors, you must send out W-2s and 1099-NEC forms by January 31, 2026. Copies also need to be filed with the IRS. Missing this deadline can lead to penalties.
- S Corporation and Partnership Tax Return Deadline (Form 1120-S and 1065): The standard filing deadline (without extensions) for S corps and partnerships for the 2025 tax year is March 15, 2026.
- C Corporation and Sole Proprietor Return Deadline (Form 1120 and 1040 + Schedule C): Even though it’s further out, flagging April 15, 2026, as the “next big one” can help business owners plan ahead for filing their 2025 return.
The bottom line
When you’re a business owner, your calendar’s already packed with project deadlines, client calls, payroll, inventory–the list goes on. Add IRS deadlines to that mix, and it’s no surprise that only 1 in 3 small business owners feel prepared for tax season.
And you know what happens when you’re not prepared? Missed deadlines, filing mistakes, and lost tax-saving opportunities that could’ve helped your bottom line. So instead of trying to shoulder it all yourself, let experts take the bookkeeping and tax work off your plate.
At CoCountant, we understand that as your business grows, staying on top of your finances and tax obligations becomes more complex and critical. That’s why we provide bookkeeping and accounting services tailored to your unique needs.
Here’s what our team can offer to growing businesses like yours:
- Precise, real-time financial tracking that gives you clarity and control over your cash flow
- Proactive quarterly estimated tax calculation and alerts to prevent surprises and penalties
- Tax planning and advisory services that stay aligned with your books, your business goals, and the law.
- Strategic identification and documentation of every possible deduction to maximize your tax savings
- Ongoing compliance to keep your documents audit-ready year-round
FAQs
What happens if I miss an estimated tax payment?
Missing a payment can result in penalties and interest. The IRS charges for underpayment, and the longer you wait, the more it adds up. Try to pay as soon as possible to minimize the damage.
Do I still need to pay taxes if I file an extension?
Yes. Filing an extension gives you more time to file your return, not more time to pay. You still need to estimate and pay any taxes owed by April 15 to avoid penalties.
Can I change my estimated payments throughout the year?
Absolutely. If your income changes mid-year, you can recalculate your estimated taxes and adjust your payments accordingly. Just be sure to stay aligned with IRS expectations to avoid penalties.
