Even if you paid on time by April 15,
If you do not pay enough tax, you may have to pay a penalty for underpayment of estimated tax. Even if you are getting a refund you can still owe a penalty for not paying in evenly during the year.
Did Turbo Tax calculate an estimated penalty?
The amount Turbo Tax calculates on your return 1040 line 23 is only an estimate. Turbo Tax can not figure it accurately because they don't know exactly when the IRS or state will get your return and tax due payment. It's very common and normal and expected for the IRS or state to bill you for more or send you a refund.
IRS info on Underpayment Penalties..
http://www.irs.gov/taxtopics/tc306.html#skiptocontent
