08/06/2026
Q3 estimated taxes are due Tuesday, September 15, which is sooner than it feels when you're running a Cape Cod business through the heart of the summer season.
Here's the situation we see most often: an owner missed the June 15 Q2 deadline, didn't realize, kept rolling through July and August, and now faces interest and penalties on top of two stacked quarters by the time they sit down with us in October.
The IRS calculates penalties from the day each quarter was due, not from when you finally pay. Skipping a quarter doesn't push the problem out, it just adds to it.
If June 15 slipped past you, the cleaner approach is to pay both quarters before September 15 lands. We wrote up what actually happens when Q2 gets missed here: https://www.stevenmellardcpa.com/bookkeeping/what-happens-if-you-miss-q2-estimated-tax-deadline/
Need help running the number for September? https://www.stevenmellardcpa.com/contact/