I cashed in savings bonds so i now have an unusally high interest income amount. Will I be subject to a penalty if I am under withheld?

[jerry2000]

That depends on how much tax you owe when you file and some other factors. You can find the complete rules in IRS Form 1040-ES at this link:

https://www.irs.gov/pub/irs-pdf/f1040es.pdf

[mkgkrause2]

additional taxes should be in the neighborhood of 3000-3500.

[jerry2000]

Carefully read the instructions for Form 1040-ES at the link I gave you. That will tell you what, if anything, you need to do.

[Hal_Al]

Simple answer: No. When there is a jump in income from the previous year, you will not owe a penalty because you had  a big amount of tax due.

The more complicated answer is: it depends on the details. If your withholding for 2017 is equal to or more than the tax for 2016, there will be no underpayment penalty (the 100% of previous year rule). Even if you owe an underpayment penalty, the penalty is minimal because it is calculated on the 100% of previous year rule.

[SweetieJean]

It's 110% if  the adjusted gross income shown on your 2016 return is more than $150,000 ($75,000 if married filing
separately for 2017).