I converted a traditional IRS to a Roth in December and Turbo Tax calculated a penalty. Without the conversion I would not owe taxes.

[loubythec]

Why is Turbo Tax calculating a penalty for insufficient withholdings when I converted a traditional ira to a Roth in December. Without the conversion I would not owe taxes.

[dmertz]

IRS Tax Topic 306 explains why you might be subject to a penalty when you do not have a sufficient amount of taxes withheld or estimated tax payments made throughout the year:  https://www.irs.gov/taxtopics/tc306.html

Because your distribution was made late in the year, you likely can reduce or possibly even eliminate your penalty by "annualizing" your income and tax payment, but the process is onerous.  You do this in TurboTax by visiting Other Tax Situations -> Additional Tax Payments -> Underpayment penalties.