09/11/2026
Filed an extension? October 15 matters.
An extension gave you more time to file, not more time to pay.
If you owe and miss the filing deadline, you could potentially add failure-to-file penalties, interest, and additional late-payment charges to an already existing balance.
Waiting until the next tax season does not reset the clock.
Get the return filed, find out exactly what you owe or are due, and deal with the situation while you still have time.