The deadline to file your taxes with the Internal Revenue Service is Monday. If you fail to file your federal tax return on time, the standard penalty is 5% of any tax due for every month the return is late, up to 25% of the unpaid balance. If you file a return but fail to pay any taxes you owe, or if you get an extension, you typically face a much smaller monthly penalty of 0.5% of any unpaid amount.
