RayW7's answer is incorrect and may cost you penalty and interest if followed. If by January 15, 2021 you do not meet either the safe harbor of having paid 100% of last year's tax liability (110% for those with higher AGI) or the safe harbor of having paid 90% of your 2020 tax liability, you must make a fourth quarter estimated tax payment. The deadline for making a fourth quarter estimated tax payment needed to avoid an under-withholding penalty is January 15, 2021.
