Extension Deadlines Are Here: What You Need to Know About Filing and Penalties

For many business owners and individuals, the fall marks more than just the end of summer—it also signals the final countdown for tax extensions. If you filed for an extension earlier this year, those deadlines are quickly approaching. Missing them can lead to costly penalties that compound month after month, so now is the time to take action.

Upcoming Deadlines

• Sept. 15, 2025: Final deadline for S-corporations and extended partnerships.

• Sept. 30, 2025: Final deadline for estates and trusts.

• Oct. 15, 2025: Final deadline for C-corporations and personal returns.

• Nonprofits: The extension deadline falls six months after the organization’s initial due date.

Failure-to-File Penalties
Penalties vary depending on the type of return, but they all share one thing in common: they add up quickly.

• S-Corporations (Form 1120-S) and Partnerships (Forms 1065/1066/8985):
  The base penalty is $245 per shareholder or partner, per month, for up to 12 months. That amount is multiplied by the number of shareholders or partners during the tax year, making the cost significant if deadlines are ignored.

• Individuals and C-Corporations (Forms 1040 and 1120):
  Failure to file results in a penalty of 5 percent of unpaid taxes per month. If the return is 60 days or more overdue, the minimum penalty becomes the lesser of $510 or 100 percent of the unpaid taxes. On top of that, the IRS adds a monthly 0.5 percent late payment penalty.

• Nonprofits (Form 1040-N):
  The penalty is 5 percent of the tax due for each month or part of a month the return is late, capped at 25 percent of the total tax due. If the return is more than 60 days late, the minimum penalty is the smaller of $510 or the tax due.

Planning Ahead for Next Year
The best way to avoid racing the clock is to treat tax preparation as a year-round priority. Provide your accountant with the information they need early, including W-9s for contractors, bills of sale, purchase agreements, loan balances, and depreciation schedules. Keeping accurate, updated records will make filing smoother and more accurate.

Another smart move is to add early reminders to your calendar. If you know returns are due, plan to have your documents complete well before the deadline so you are not caught in a last-minute scramble.

The Bottom Line
Extensions buy time, but they do not erase the responsibility of filing or the penalties that come with delays. With the September and October deadlines now in sight, double-check your records and make sure your return is ready to file. The effort you put in today can save you from expensive penalties tomorrow.