I updated 2018 Home & Business on 1/18/219 but the program will not let me update the amount paid for primary home property tax.

What is happening when you go back through the interview to change it?

....does the exact text "$0" show on that entry line?

yes - and it won't change - just stays $0

Whenever you see that "$0"  (an actual zero)...a "Supporting Details" sheet is attached to that entry, usually transferred in from last year, but after the actual $$ entries were stripped out.

Problem is that TTX reprogrammed that page such that the "Supporting Details page doesn't pop up like it used to...so three ways to work around  it until they get it fixed (been reported).

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Here's what I think is happening...and how to fix it.

1)  In 2017 you added "Supporting Details" to each of those fields where you encounter a locked "$0"...probably to describe  when & how paid it in some prior year.

2)  The Supporting Details sheets (empty) transferred into your 2018 file from your 2017 file.

3)  The Supporting Details are supposed to pop up as soon as you attempt to enter a value during the Interview...but it doesn't.  (Software Bug)

4) Workarounds  : 

4a)  double-click in the field and the Supporting Details sheet pops up and you can either delete it (hit the big red "X"), and now make an entry...or you can use the SuppDetails worksheet to enter your $$....OR...

4b)   Put your cursor in the box, click, and then go to the top menu on the screen and click on <Edit....then <<Add Supporting Details from the drop-down menu.  IF the SuppDet box shows up you can either add your entry in there...or hit the Red "X" to delete the whole SupDet worksheet and then make your normal entry.....or...

4c)  Put your cursor on the box, click....then switch to Forms Mode...., and enter the payment  directly in the worksheet.   You can also delete the Supporting Details sheet entirely (look for the REMOVE "X" when it pops up)..once that is done, you can make entries using the interview again..

(been reported too, but might take weeks to fix...or never since we've heard nothing yet)

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and the are other places ..like Medical Expenses and Federal Quarterly Tax payments...where the same "$0" issue may pop up

Hey, guess what?  The same bug is present in Turbo Tax 2019!  The idiots didn't fix it.

Thanks for posting the workaround.  

I had this exact same issue occur with 2020 TurboTax Deluxe -- it would not let me enter the amount paid for home property tax -- and the recommended solution worked:  "double-click in the field and the Supporting Details sheet pops up and you can delete it ".

In TurboTax Deluxe 2020, you have to switch to "Forms" mode to update the supporting data field.