I have filed my 2019 return with a download version of Basic edition ($39.99), I do not have to file a state return (live in Washington state).
Before filing I created a copy of this file for experimental purposes.
Now I want to experiment to see what a state filing (for a state other than Washington) would do to my tax liability, so in the (unfiled) experimental copy I asked to do my state return. TTax told me I need to upgrade (of course), but that it would be $45 per state. All I want to do is upgrade to Deluxe, which should only cost me $20, shouldn't it? (I have my purchase confirmation code, but TTax doesn't let me do it).
You would need to purchase a new package as if you never filed your return. You cannot upgrade after filing and only pay the difference in pricing.
Actually, I was able to upgrade after filing! However, it cost me $30 , which, in addition to the Basic purchase price of $40 came to $70 total (as opposed to $60 for an original purchase of Deluxe, if I'd been clearer at the outset). Still, it's better than $40+$60= $100.