Traditional IRA Basis

A traditional IRA has no basis, all withdrawals are subject to regular income tax.  If you have tax withheld from your withdrawals, that is only an estimate.  Your final tax owed is calculated on your tax return and you get credit for any withholding.  If you still owe more tax, that means you did not have enough withholding. 

@Wolfman32 

Do you have an actual basis in your Traditional IRA, as reported on a previous Form 8606?

If so, you have to tell TurboTax about it.