Deductions & credits

This is kind-of a tough one to answer as a "for sure" situation....I'll give you my analysis, but you might need to call TTX Customer Support to be sure....and even then, it might take them some time, and a diagnostic file form you, to figure it out.:

https://ttlc.intuit.com/community/using-turbotax/help/what-is-the-turbotax-phone-number/00/25632

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But here's my analysis.  I've noticed in the past couple years, that if a person files a tax return, and then a later software update changes the results, using data that is already in the tax return, that the software seems to keep track that the software change itself has changed the original tax file. Such that, if you start an amended tax return and do nothing else, the amended refund (or balance owed) will immediately show in the refund meter. 

Thus an amended tax return with the updated 2018 software would show that refund for you right away, as long as you had already entered the the Form 5695 data into the original tax return at the time you filed the first one  (sounds to me like that is what you did).

The original 2018 software, before the update, did  allow you to enter the energy credits because some states have energy credits too, even though the Feds didn't allow some until much later legislation which back-applied to 2018.  And he original software did allow you to enter all of the various "costs" for Residential Energy Credits, even if there was no credit. 

((I don't recall whether this was something that TTX did, or whether the IRS left the form 5695 entries unchanged (without applying an actual credit), because the IRS may have fully expected Congress to do something...even if horribly later....also, their software already had the full form 5695 programmed ...so why fully redesign it.))

>>>AS far as knowing whether your original tax filing had the credit in there or not, you need the Printout, or Original PDF file from when you actually filed your taxes (not a PDF or printout from after the software was updated).  The TTX software update for those energy credits didn't occur until a couple months into 2020, but I'm not sure of the exact date.   So if you have a copy of that original tax filing...look for an entry on line 53 of the Schedule 3.  That's where the energy credit would show up.  If that line, or the entire Schedule 3 is missing from your original 2018 tax return, but is present in the Amended tax return you just started, then yeah, your amendment should be OK, and the additional refund $$ should be showing on line 21 of the 1040X.

IF the additional refund is showing on that line 21, I have no idea why the software says there is no change, because there is.  But that may be more of subtle software confusion with the update not quite tracking everything since the form 5695 was already in there.  You should probably step thru the Energy Credits interview carefully again to make sure it's all set properly

BUT, you should also enter an explanation for the change in PART III of the 1040X...something like "Added  correct updated Form 5695 Residential Energy Credit" .    Normally, that is asked for as soon as you start an amended tax return, but if you didn't put something like that in , you can add it in by switching to Forms Mode  (desktop software) and opening the form 1040X and scrolling down to Part III, and you can enter it directly in the form.

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Be sure to go thru the full filing process (Mail-file only) so that software prints out only the forms you need to file....and it will display the address you need to mail them to on the filing instructions sheet that prints.