My "tax outcome" does not add up. My total amount of federal taxes owed, minus taxes withheld and the federal credits, does not equal my taxes owed. Why is that?

[Vanessa A]

How are they not adding up?  Which line are you looking at?

Do you have self-employment income?  

Do you have non-refundable credits?  If so, this will only reduce your tax liability to $0.  So if you have $5,000 in nonrefundable credits, and only $3,000 in tax liability, you would only get a $3,000 credit, not the full $5,000. 

[VolvoGirl]

Is the Tax Due on line 37 too much?  Check line 38 for a penalty.

You might be able to eliminate it or at least reduce it. You can go to Federal Taxes tab or Personal tab, under Other Tax Situations and select Start by the Underpayment Penalties. You will answer a series of questions that may reduce or eliminate the penalty. Or you can elect to have the IRS figure the penalty for you. It's form 2210.

How to add form 2210 for Underpayment Penalty
https://ttlc.intuit.com/community/tax-payments/help/how-do-i-add-form-2210/00/25703

It's under

Federal or Personal (for Home & Business Desktop)

Other Tax Situations

Additional Tax Payments

Underpayment Penalties - Click the Start or update button