Generally, exemptions from penalty will apply if:
In 2017 or 2018, you retired after reaching age 62 or became disabled, and your underpayment was due to reasonable cause (and not willful neglect), or
The underpayment was due to a casualty, disaster, or other unusual circumstance, and it would be inequitable to impose the penalty. For federally declared disaster areas, see Federally declared disaster, or
The underpayment was due to an inability to accurately calculate your estimated income tax payment due to the breadth of changes enacted by tax reform.
