Penalties for filing personal return late

Late payment penalties apply if you didn't pay taxes owed by the deadline,  regardless of whether you filed an extension or not.

The late payment penalty is 0.5% (1/2 of 1 percent) of the additional tax owed amount for every month (or fraction thereof) the owed tax remains unpaid, up to a maximum of 25%.

If you cannot afford to pay all of what you owe now, you should file your return or extension. pay what you can and then pay whatever balance you have as soon as you can to minimize any penalties and additional charges you might incur.