09/01/2026
September 15th isn’t just “another tax date.” If you’re self-employed, this one can actually cost you if you miss it
Here’s what’s due:
→ Q3 2026 estimated tax payment
→ Extended deadline for S-Corp and partnership returns
Miss the estimated payment and the IRS can charge you a penalty, even if you pay in full come April. Miss the extended business return deadline and it’s a flat penalty per month, per partner or shareholder, on top of whatever you already owe
Swipe through for exactly who this applies to and what to do before the 15th
08/24/2026
08/06/2026