To avoid a penalty you just have to pay ...
· Your
taxes withheld don't cover at least 90% of what you owe for 2017, or
· Your
taxes withheld aren't at least 100% of what you owed for your 2016 taxes, if
your adjusted gross income (AGI) is up to $150,000, or
· Your
withholding is 110% if your AGI is more than $150,000. (The AGI amount is
$75,000 if you're married filing separately.)
So you don't need to know what your 2017 income will be ... just base the estimate on your 2016 tax liability.
