there is a safe harbor that if you meet it avoids underpayment of estimated taxes even if you owe a fortune come next 4/15. this avoids the need to CALCULATE current year quarterly estimates. However, you could end up significantly overpaid
timely estimated tax payments and withholding = 100% of your 2024 tax. that 100% jumps to 110% if your 2024 adjusted gross income was $150K or more. you can use 1/4 of annual withholding for each period or use actual for every period
other safe harbors
withholding
1) and timely estimated tax payments equal or exceed 90% of your 2025 tax or
2) the balance due after subtracting taxes withheld from 90% of your 2025 tax is less than $1,000 or
3) your total 2025 taxes are less than $1,000
for states each has their own rules that should be checked
