I wanted to start a dedicated thread for this topic, as it is somewhat off the main path and being lost elsewhere. I believe that the approved Senate bill contains erroneous numbers for the revised AMT. I'll illustrate below:
Example: married, filing jointly, no deductions beyond the new $24K standard deduction
Normally, we would not expect such a person to be subject to the AMT, as it is intended to claw back excessive deductions and loopholes to ensure everybody pays a "fair" tax. The approved Senate bill provides two updated numbers:
AMT exemption: $109,400 (up from $86,200 otherwise scheduled for 2018)
AMT exemption phaseout threshold: $208,400 (up from $164,100 otherwise scheduled for 2018)
The bill is silent on the threshold for the 28% AMT bracket, so we'll assume it remains at the inflation adjusted 2018 value of $191,500
I set up a spreadsheet to calculate regular tax and AMT tax at various AGI values for the hypothetical taxpayer outlined above. My analysis shows that such a taxpayer will pay AMT for all incomes between $294265 and $758443.
This can't be correct, can it? We already know through the media that they messed up the corporate AMT (making the AMT calculation the same as the normal tax rates). I would like to believe that they did the same with the individual AMT and will have to "fix" it in committee. Otherwise, the cuts to all of the normal brackets are worthless to a MFJ taxpayer, with no deductions, making between $294K and $759K. Maybe that's middle class. Maybe not. But it is a huge swath of taxpayers who would see little benefit other than the moderately expanded AMT exemption.
I would greatly welcome hearing what others, interested in the AMT, have learned about this.