Subject: Re: Finally got it right
Even if you underestimate and owe more it's generally not a big deal, if you are reasonably close.

The penalty is calculated on the difference between what you had withheld and the lowest safe harbor amount. Reduced by the $1000 threshold.

Turbotax will figure your penalty and include it in what you owe.

But you can tell Turbotax to ignore that and let the IRS figure it out and send you a letter. Which they might not actually ever get around to. ;-)