September 15 is coming up, and there are two federal tax deadlines that construction and contractor business owners may need to be aware of.
The first is your third-quarter estimated tax payment. The second applies if your S Corporation or partnership tax return was extended earlier this year. Both are on our full 2026 tax calendar if you want the rest of the year's dates.
1. Third Quarter Estimated Taxes Are Due September 15
As a business owner, you generally need to pay income taxes throughout the year as you earn money rather than waiting until you file your tax return.
For 2026, the third-quarter estimated tax payment is due September 15.
This is important for owners of S Corporations, partnerships and other pass-through businesses, and for anyone who operates as a sole proprietor. Your company may be doing well and showing a nice profit, but that profit can also create a personal tax bill for you.
Depending on your situation, your tax accountant may have already given you estimated tax vouchers or payment amounts for the year. If so, now is a good time to review those and make sure the September payment is taken care of.
The IRS gives you a few easy ways to make an estimated tax payment:
- IRS Direct Pay: Pay directly from your checking or savings account at no charge.
- IRS Online Account: Make payments and review your payment history online.
- IRS2Go: The IRS mobile app also provides options for making tax payments.
If cash is tight and you're not able to make the full payment, don't just ignore it. Talk with your tax preparer or accountant before the deadline and figure out the best way to handle it.
2. Extended S Corporation and Partnership Returns Are Also Due
September 15 is also an important deadline if your business filed an extension earlier this year.
For a calendar-year business, an extended S Corporation Form 1120-S or Partnership Form 1065 is generally due September 15.
If you're still waiting to finish the return, make sure your tax accountant has everything they need. For a contractor, that may include finalized bookkeeping, payroll information, equipment or vehicle purchases, loan balances and any other year-end information that still needs to be cleaned up.
Don't assume that being late doesn't matter just because an S Corporation or partnership may not owe much federal income tax directly. Both types of returns can have late-filing penalties that increase based on the number of shareholders or partners and how long the return remains late.
What Should You Do Now?
If either deadline applies to you, now is a good time to take a moment and ensure everything is scheduled or taken care of.
Check your estimated tax payment, make sure your tax preparer has what they need for any extended business return, and reach out sooner rather than waiting until September 14.
As always, your specific tax situation can be different depending on your business structure, income and other factors. If you're unsure what you need to pay or file, check with your tax preparer or accountant before the deadline.
