You haven't even started on your federal tax return?
Don't fret.
If you're due a refund, April 15 isn't much of a deadline at all.
The penalty is a percentage of what you owe.
The Internal Revenue Service doesn't like to talk about it, but penalties for filing late federal tax returns apply only to people who owe money.
If you owe nothing, 5 percent of nothing is ...nothing.
If you have unpaid taxes, though, the late fees add up quickly.
The IRS says about three-fourths of filers get refunds.