The most common penalties are for filing late or paying taxes late.
Filing late: If you do not file your return by the due date (including extensions), you may have to pay a failure-to-file penalty. The penalty is usually 5 percent for each month or part of a month that a return is late, but not more than 25 percent. The penalty is based on the tax not paid by the due date (without regard to extensions).
If you file your return more than 60 days after the due date, the minimum penalty is $100 or, if less, 100 percent of the tax on your return.
Paying tax late: You will have to pay a failure-to-pay penalty of ½ of 1 percent (0.5 percent) of your unpaid taxes for each month, or part of a month, after the due date that the tax is not paid. This penalty does not apply during the automatic six-month extension of time to file period if you paid at least 90 percent of your actual tax liability on or before the original due date of your return and pay the balance when you file the return.
The failure-to-pay penalty rate increases to a full 1 percent per month for any tax that remains unpaid the day after a demand for immediate payment is issued, or 10 days after notice of intent to levy certain assets is issued.
For taxpayers who filed on time, the failure-to-pay penalty rate is reduced to ¼ of 1 percent (0.25 percent) per month during any month in which the taxpayer has a valid installment agreement in force.
Combined penalties: For any month both the penalty for filing late and the penalty for paying late apply, the penalty for filing late is reduced by the penalty for paying late for that month, unless the minimum penalty for filing late is charged.
Accuracy Related Penalties
The two most common accuracy related penalties are the “substantial understatement” penalty and the “negligence or disregard of the rules or regulations” penalty. These penalties are calculated as a flat 20 percent of the net understatement of tax.