If the taxpayer did not have enough withholding or estimated tax payments and owes more than $1,000 to the IRS, he may owe an underpayment penalty may. For 2019, a taxpayer is subject to an underpayment unless total withholding and estimated payments equal the smaller of:
90% of the tax shown on the 2019 tax return, or
100% tax shown on the 2018 tax return (110% if the taxpayer’s 2018 AGI was more than $150,000 ($75,000 if his 2018 filing status was Married Filing Separately)).
The required tax payments must be paid on time.