TaxStuff - basic federal tax return calculator

NOTE: this is a work in progress; please don't file your taxes based solely on this software. I don't.

This software attempts to automate a subset of the United States Internal Revenue Service forms. The intention is to enable the user of the software to estimate their tax liability and to better understand their taxes. The software is not a substitute for something like TurboTax: it assumes you already know what forms you want to file.

I was inspired by Robert Sesek's excellent ustaxlib.

Example

Requires .NET SDK to build and run.

When you run the program, it takes two arguments: the path to the return file and a folder to put the PDFs in:

mkdir output
dotnet run --project TaxStuff/TaxStuff.csproj ExampleReturn.xml output

See example input file and example 1040 output.

Features

• Can import OFX tax exports (from Schwab for example), to support interest dividends, and stock transactions. The contents of the 1099-Bs will be turned into Form 8949s and will be referenced by 1040 Schedule D. The 1009-DIVs and 1099-INTs will be put into the right places on Form 1040.
• Fill in the results of tax computations into PDF tax forms. (only implemented for the 2020 tax year currently)
• A custom XML format and expression language for defining tax forms. See the 2023 folder for the forms.

License

I'm not really sure what to license this as right now. The dependencies has a couple of different license, which makes this more complicated.

• iText: GNU Affero General Public License

• ANTLR: BSD 3-clause

• OFX XML Schema files: Just "All Rights Reserved", though the specification says

  A royalty-free, worldwide, and perpetual license is hereby granted to any party to use the Open Financial Exchange Specification to make, use, and sell products and services that conform to this Specification.

  I don't know how "conform" is evaluated.

TODO

• More unit tests

• Support for references to previous years, to support things like capital loss carryover and Schedule J.

• Support for filling in personal information into PDFs.

• Support for filtering array values, probably using a bracket syntax. Use cases:

  • Replace the special filter function FilterForm8949 with native filitering support.

• Similar to the above filtering, support a "group by" feature.

  • For 2020 Form 1040 Schedule 3 Line 10, it would be nice to write something like:

    FormW-2.GroupBy(f => f.SSN)
           .Select(g => Math.Max(0, g.Sum(f => f.SocialSecurityTaxWithheld) - 8537.40))
           .Sum()

• Clean up PDF writing

  • Leave spaces blank when appropriate instead of writing 0.
  • Round to whole dollars.

• Somehow unify the parsing, typechecking, and evaluation representation of language semantics. Particularly EvaluationResult and ExpressionType have a similar shape.

• Improve loading time. Currently it takes 650ms to load the whole tax universe. This is because it is parsing every year (even though only one is needed) and type checking all the forms. Some ideas for speeding up include only loading the one year that is needed or somehow moving some of the parsing and type checking of XML files to compile time.

Adding support for filling in PDFs

I've only done year 2020 form 1040. The process I'm using to find the name of the fields of the PDF to fill in is:

1. Use the XfaForm iText API to pull out the XFA form template.
2. Find the assistive text associated with each field. These nodes can be found with the XPath expression form/assist/speak.
3. Record a substring of this node in the PdfInfo.xml file.

Hopefully by going by the assistive text on the PDF this mapping is a little easier to maintain than just recording the field name. The field names appear to be generated, like "f2_28".