Additional tax on IRAs usually means either you took a distribution before age 59½, you made an excess contribution, or you failed to take a required distribution (RMD). If none of these reasons make sense, then as VolvoGirl said, you might have answered a question wrong when you entered your 1099-R forms. Review the entries, including all of the follow-up questions, or delete the 1099-Rs and reenter them.
You still haven't said whether you are using TurboTax Online or the CD/Download TurboTax software. If you are using the CD/Download software, or the Online Free Edition, you can look at Form 5329 and see which section of that form the tax is coming from.
