For 2019, the deadline to file your taxes was April 15 in nearly all states. Residents of Maine and Massachusetts have until April 17, while certain other citizens, including those who live abroad and disaster victims, have longer.
If you requested an extension, which also had to be done by April 15, you'll have until October 15 to file your taxes. An extension to file, however, is not the same as an extension to pay. To avoid accruing interest and facing a late fee, you should have already paid what you owe by the deadline.
If you didn't get it done, there are a few things you need to know to avoid some potentially serious penalties.