Does the current TAXSIM executable leave out the 2023 Missouri Working Family Tax Credit?

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
28/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Active
Tech stack
python
Domain
backend

Research direction

The discrepancy is in the Missouri v39 working family credit for 2023 records, and the Windows executable also fails on census record 16099 with an index error at line 20672 of taxsim.f. Start by running the sample CSV rows through the emulator and the TAXSIM executables to reproduce both the zeroed 2023 credit and the 2022 crash. Done means the emulator's 2023 Missouri output matches the statute's 10% rule, or the upstream cause is identified, and the crash has a reproduction. The fix may belong in PolicyEngine's Missouri parameters, not this repository.

Written by the indexing model from the issue text.

Description

The current TAXSIM executable gives v39 = 0 for 2023 Missouri records. The previous TAXSIM executable gave 10% of the federal EITC (limited to the tax), as PolicyEngine does. 2024 and 2025 (20%) are unchanged, and 2022 is 0 in both executables.

taxsimid,year,state,mstat,page,depx,age1,age2,pwages,idtl,opt1,opt1v
1,2023,26,1,36,2,10,12,40000,2,30,1
2,2024,26,1,36,2,10,12,40000,2,30,1
id year federal EITC v25 TAXSIM v39, previous / current PolicyEngine v39 TAXSIM fiitax / siitax TAXSIM siitax, previous executable PolicyEngine fiitax / siitax
1 2023 2,720.54 272.05 / 0.00 272.05 −4,730.54 / 673.61 401.56 −4,730.54 / 426.19
2 2024 3,320.83 600.02 / 600.02 622.11 −5,479.83 / 0.00 0.00 −5,479.83 / 0.00

In row 2, 20% of the EITC (664.17) is more than the tax, so v39 is the tax. In row 1, the $24.63 gap that stays between the previous executable and PolicyEngine comes from Missouri taxable income (v36 17,302.50 vs 17,800). That is a separate item.

2023 Form MO-WFTC, PDF page 2: "The Missouri Working Family Tax Credit is equal to 10% of your Federal Earned Income Credit for tax year 2023. The credit cannot be refunded and cannot be carried forward to a subsequent tax year."

Census impact: 5 Missouri 2023 records lose the credit ($49.68 to $401.58), and 3 of them are now above our filing threshold.

The current Windows executable (same build stamp) stops on 2022 Missouri records, for example this census record:

taxsimid,year,state,mstat,page,sage,depx,age1,age2,age3,pwages,dividends,intrec,idtl,opt1,opt1v
16099,2022,26,2,36,37,3,8,3,1,59923.80952380953,182.7485148514852,496.2983774551665,2,30,1

At line 20672 of file taxsim.f
Fortran runtime error: Index '2022' of dimension 1 of array 'disqa' below lower bound of 2023

The macOS and Linux executables run this record without a message. This may be the same change.

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