Tax Planner, that time of year

Deadeye

It's that time of year to adjust your tax basis and deductions as you can in the last quarter. My goal is always to have zero payment, zero refiund through tweaking my 401k withholding and/or my tax withholding.
There is a bit of a discrepancy betwen the tax planner and the IRS tax calculator, of about $2k.
Tax planner says I will owe, IRS says I won't. This issue has been persistent since about Quicken 2008 or so. Sometimes it goes one way sometimes the other, and I always itemize, and always accurately reflect my income. With all of the recent tax changes I'm not sure which to believe, if you miss itemizing it's a big tax hit.
So the question is, not which is right, but if anyone knows does the Tax Planner default to standard deductions now, or is it calculating my itemizing?

thanks.

Sherlock

The Tax Planner will use the standard deduction if the estimate of the itemized deductions are less.