Karen,
Thank you for this detailed explanation, it is clear.
I finished my amended tax return following what the software tells me to do. I think TurboTax has a bug.
Federal:
* Original return I had a 8K refund, which I applied to 2018 estimated tax (1040 line 77).
* Amended return TurboTax asks me to pay $5K, but now there's only $3K applied to 2018 (1040 line 77), and it shows I overpaid $3K (1040 line 75) and that I owe nothing (1040 line 78) with no tax penalty (1040 line 79).
=> 1040 looks correct and 2018 estimated tax was corrected to owe nothing, BUT TurboTax reports I should pay $5K.
So if I pay the $5K and the 1040 doesn't apply the $5 to 2018, it means TurboTax accounting might off when I file 2018. Hopefully IRS accounting would catch it and apply the $5K to my 2018 refund if I send the check?
California:
* Original return I had $2.2K applied to 2018 estimated tax (540 line 95)
* Amended return still has $2.2K applied to 2018 estimated tax (540 line 95)
* Amended return shows I overpaid $500 (540 line 94)
* Amended return asks me to pay $1.7K (540 line 114)
=> This looks correct but 2018 estimated tax was not adjusted.
Following your advice I should not change line 95 to $500, which would adjust line 114 to zero?
I think this requires filing a bug report on TurboTax. Note I have $500 of AMT due which might have thrown a wrench in the accounting logic.
Sorry this is long 🙂
