I am trying to override form 1040 line 12, I right click the mouse, the override menu shows up, but it's greyed out, so I am not able to override, how to fix this?

Form 1040 Line 12 is the taxes on taxable income and cannot be over-ridden.

What exactly are you trying to accomplish?

1040 line 12 is the tax on your income.  What is wrong with it?  You change the tax by changing the income, deductions or adjustments in the lines above.  Which you do by changing your entries.  I don't think you can make overrides in the Online version, only in the Desktop program anyway.

Then it depends on what kind of income you have, if you have capital gains or qualified dividends the tax on line 12 is not taken from the tax table but is calculated separately from schedule D.  The tax will be calculated on the Qualified Dividends and Capital Gain Tax Worksheet.  It does not get filed with your return.  In the online version you need to save your return as a pdf file and include all worksheets to see it.

For the Desktop version you can switch to Forms Mode and open the worksheet to see it.  Click Forms in the upper right (upper left for Mac) and look through the list and open the Qualified Dividends and Capital Gain Tax Worksheet. 

For me, Schedule A line 17 is $9051, BUT when transfered to 1040 line 12, it shows up as $14,050.  This is INCORRECT and instead of getting money back, as Turbotax indicated, I OWE the IRS money.

What when wrong in Turbotax?

Something else is going on.   14,050 is the Standard Deduction  for Single over 65.   It is more than your Itemized Deductions so you get the Standard Deduction.   And having a larger deduction should increase your refund not reduce it.  The IRS changed something else.   

Thanks, that makes sense.  However it does not resolve the issue where Turbox tax says I'm gettin >$1000 back and the IRS says I OWE them

A common adjustment is if you claimed the Recovery Rebate Credit on 1040 line 30 when you already got the Stimulus payments or got the second one after you filed or reported the wrong amounts. Do you have an amount on line 30? And you had to report the right amount in each box. If you put the total in 1 box it would give you the other amount again. The IRS knows they already sent it to you. Line 30 is only if you qualify more.