If you didn't get a letter from the IRS how do you know line 38 is wrong?
The amount Turbo Tax calculates on your 1040 line 38 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.
You might have been able to eliminate it or at least reduce it. You go to Federal Taxes tab or Personal tab, under Other Tax Situations and select Start by the Underpayment Penalties. It's from 2210.
