The IRS is automatically waiving an estimated tax penalty for eligible 2018 tax filers. The waiver applies to taxpayers who paid at least 80% of their total tax liability through federal income tax withholding or quarterly estimated tax payments. When they filed their 2018 returns, these taxpayers didn’t claim an available special waiver put in place because the Tax Cuts and Jobs Act caused many people to not have enough tax withheld. The waiver provides relief to those who filed too early to take advantage of it or was unaware of it when they filed. Eligible taxpayers who paid the penalty will receive a refund check about three weeks after they receive a “CP21” notice in the mail.