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.
See https://www.irs.gov/taxtopics/tc306
