IRS Underpayment Penalty questions?

1 big exception is if you had withholding equal to your last years taxes,. There are exceptions if there was a year end bonus that was paid that caused the underpayment. The penalty can be computed on form 2210, but the IRS will send you a notice and give you about 30 days to pay without additional interest. The penalty on 1400 should be less than $15, but it is likely you had more than 90% of your tax liability withheld or the withholding was equal to last years taxes which negates any penalty.