If you already filed your 2018 tax return and paid the underpayment penalty, you can request a refund of the penalty by filing Form 843. Include "80% Waiver of estimated tax penalty" on line 7.

For those who already filed their tax return and included the penalty, the penalty can be abated by filing Form 843, Claim for Refund and Request for Abatement. When filing Form 843, make sure you ...