The key is to avoid a penalty for underpayment of estimated tax.
You can avoid that penalty if:
1) You owe less than $1,000 in tax, after subtracting any withholding and refundable credits, OR
2) You paid withholding and estimated tax of at least 90% of the tax for the current year or 100% of the tax shown on your return for the prior year, whichever is smaller.
The key is to avoid a penalty for underpayment of estimated tax.
You can avoid that penalty if:
1) You owe less than $1,000 in tax, after subtracting any withholding and refundable credits, OR
2) You paid withholding and estimated tax of at least 90% of the tax for the current year or 100% of the tax shown on your return for the prior year, whichever is smaller.
If you don't pay the estimates and your withholding isn't any of the following you will be hit with underpayment penalties.
1) 2020 balance due after withholding is less than $1000
2) withholding covers 90% of 2020 tax
3) withholding is 100% (110% if 2019 adjusted gross income is over $150,000) of 2019 tax
See this for calculating 2020 estimated taxes - https://ttlc.intuit.com/community/tax-payments/help/can-turbotax-calculate-next-year-s-federal-estim...
See this for paying estimated taxes - https://ttlc.intuit.com/community/tax-payments/help/how-do-i-make-estimated-tax-payments/00/25875