I was going to go into detail on this issue but will start with the basics and add as necessary.
In 2019 for some reason when I filed my prior year tax credit ($2629 from 2018) got counted twice so instead of my estimated taxes being $5364 they were $7993 on line 8 of Schedule 3 of 1040-SR. IRS caught this and sent me notice that my refund I wanted to credit to 2020 was reduced from $3093 to $464 -- in IRS systems, that is. I did not amend my 2019 return in Turbo tax which was why I imagine this error carried over to 2020. IRS sent me similar letter in 2020 saying I had underpaid my taxes which was true because Turbotax overstated the size of my refund from 2019 (3093 instead of 464) which I had not told Turbotax about because I did not amend the 2019 return. I just paid the tax and did not amend my 2020 return. I don't want to make the same mistake for 2021. What is the best way to clean this up?
