How do I know how much the IRS thinks I owe in taxes?

[sethmachine]

I filed taxes for the first time in 2015 using the Turbotax. It comes up with "estimated taxes."

If however I don't pay all the taxes the IRS thinks I owe by the April 15th due date, they will bill me for the remainder with interest penalties.

My question is, if my tax software fails and underestimates how much I owe, what can I do to protect myself from penalties for underpaying?

How do I know what the IRS thinks is my tax liability before getting a penalty?

[scfr]

For US tax related questions, the IRS web site has a lot of information.

https://www.irs.gov/taxtopics/tc306.html?_ga=1.44169764.1631769493.1472328288

Were your estimated taxes based on 100% of your 2015 taxes?

[MakeAStash]

Usually if by year end you pay (or have withheld) taxes at least equal to the amount paid the prior year (100%) you will not be hit with an underpayment penalty. There are some situations in which 90% is sufficient and others in which 110% must be paid, so you should read up on the details.