There are two safe harbors, meaning that if you meet either, you can't be penalized for failure to pay 100% of your 2025 taxes.
1) withholding is 90% or more of your 2025 tax. With the possibility of substantial tax law changes, there is no way to know what this would be.
2) withholding is 100% or more of your 2024 tax. This rises to 110% or more if your 2024 adjusted gross income was $150,000 or more. You can always pay in more, so there isn't a big tax bill come 4/15/2026
withholding is better than estimated tax payments because there are two options for how to handle withholding for penalty purposes
a) the default is that 1/4 of the year's total is deemed paid each period, regardless of when actually withheld
b) you can use actual withholding for each period
on the other hand, estimates only count for the period in which they were made
you also have the option of using the 2210's annualized installment method to calculate what needs to be paid in for each period. however, with possible substantial changes in the tax laws for 2025, that haven't yet been passed, this method is currently a crap shoot.
