Tl888,
Understand the frustration. The advice I had was for the Form 1116 itself as I did not have any AMT issues.
The keys remain: (1) Change at the 1099 level for each 1099 showing foreign income or tax, (2) no "various" for dates or country should survive in 1099 Box 8, consistent confirm the nature of the income (most of us just have mutual/stock dividends and "RIC" works best as true (3) If mutual funds (again, most of us) check the 1099 Box 8. (4) Confirm no "various" has survived and is being shown in the Form 1116 itself. Part I, i (Enter name of foreign country; for me with mutual fund foreign tax using RIC from the dropdown menu worked); Part II Country (L) Date Paid are prime suspects. It can take an auditor's diligence and attention to detail to crack this monster.
NOTE: I have not tried this on other than passive income. However, if you filed a Form 1116 last year for the same type of income (again, I only had passive income), compare each individual line with this year (yes, a pain to do. Took me 7 failed attempts to learn to do that before #8 was successful.) It could be one of the boxes is not checked or line filled in differently on the Form 1116 for 2020. The error there could carry over to the Form 1116 AMT. If you are using the Simplified AMT (most do) you should not have to make any entries on the Form 1116 AMT.
