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Fix erroneous federal AMT calculation #4775
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Does this relate to PSLmodels/Tax-Calculator#2785? |
@MaxGhenis asked in PR #4775:
No. |
Thank you @martinholmer for filing - The issue here is that we do not consider capital gains taxes when computing the final AMT amount in Part II Line 10 - will fix now |
@PavelMakarchuk said in issue #4775:
Good that you've identified the problem in the code. |
This reform simulates repealing AMT by raising the exemption to $1T: https://policyengine.org/us/policy?focus=policyOutput.policyBreakdown&reform=62899®ion=enhanced_us&timePeriod=2024&baseline=2 Before merging #4815, this produced a $153 billion cost in 2024; now it's $0.8 billion. Do we now need to adjust other parameters to simulate AMT repeal? We could also try neutralizing from a notebook. Other reforms still work correctly, e.g. TRAFWA. |
I wonder if the previous effect was correct - the easiest way it to set the rate to 0 (both brackets). This would produce an impact of $1.4 billion - which is what we get if we repeal the AMT as a structural reform |
TPC projects that AMT raises $6.3 billion in 2023 I would expect our projection to be lower as we haven't fully incorporated important deductions like the property tax component of SALT and charitable deductions. So $1.4 billion seems OK. Do you know why an infinite exemption differs from zeroing out the rates though? |
There is a cap on the exemption amounts for filers who are below 18 |
The following simple 2022 test case illustrates a major flaw in the federal AMT calculations that can cause PolicyEngine-US to generate federal income tax amounts that are many thousands of dollars larger than the correct amounts. This flaw causes errors as far back at 2018 (see #4769).
The characterization of this situation as a bug seems sensible because online TAXSIM-35 and Tax-Calculator 4.2.0 and 2022 Turbo Tax are all in agreement that this test case has a zero AMT. PolicyEngine-US 1.28.0, however, generates a federal AMT amount equal to $7,538.50.
That this bug exists is not particularly surprising because the developers of the
alternative_minimum_tax
formula did not specify any unit tests for it. (At least, I can't find any tests when doing a recursive grep operation over the source code tree.). Also, the 2022 federal income testing done in issue #1773 never considered test cases with more than $10K in qualified dividends or more than $10K in long-term capital gains.First, I show the YAML file containing the test case. Then I show several screenshots from Turbo Tax processing a make-believe person like the test case.
The YAML test case:
2022 Turbo Tax screenshots:
.
.
And finally, federal Form 6251:
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