If you follow my example calculation in the post above, it will tell you what it's doing. In short, the amount it transfers to line 14 in the Utah form is $10,000 - Ut State Real Estate Tax (Line 5b on Schedule A), and calls that my UT state income tax deduction. It doesn't apportion anything as described in the help file.
So, in my example above of $3000 in Property Tax, Turbo Tax reports $7,000 as my State Income Tax deduction on Line 14. That is, simple subtraction ($10K -$3K = $7K), not an apportioned amount.
In my personal case, it under-reports my deduction if the apportionment method were to be valid (not sure it is, but the Help file says that's what the SW is supposed to do. Also, no idea if the simple subtraction method is valid, but both seem reasonable given the Federal limit of $10K.... just not sure what in the tax code Turbo Tax is using to justify either the method described or the method apparently implemented). Ultimately, for me, it has no effect on my return as the only thing it impacts is calculating the state tax credit, which I don't qualify for anyway. However, it does seem like an anomaly in the software..
I just ran another test case where I changed the property tax value to be $4,000 on Schedule A, and Line 14 on TC-40 now shows $6000 as my deduction. Turbo Tax is not behaving as described in it's own Help file. It's a pretty easy test to configure.
