Open-source Tax Solver (OTS)

January 26, 2016
- Project -

OpenTaxSolver (OTS) is a free program for calculating Tax Form entries and tax-owed or refund-due, such as Federal or State personal income taxes.  

Updating OTS for the current 2015 Tax Year is underway. Initial release is expected by early February. As in prior years, the update will cover the US 1040 with Schedules A, B, C, D, along with the 6251 (AMT) & 8949 forms. We are looking for volunteers to help in updating the State Tax forms for California, Pennsylvania, New Jersey, North Carolina, Ohio, Virginia, New York, and Massachusetts, as well as submitting programs for other states.

New Mailing List:
The former website we previously used for issuing announcements of updated releases and fixes is now defunct. Therefore, we now have a new mailing list you can join for OTS News. See the link at the bottom of this main page, or here Subscribe to New OTS Releases & Updates. (You can remove yourself from the list at anytime by sending an email from your email account to with the words "Remove me." as the first words in the subject line.)

Automatic PDF Forms Fill-out:
An experimental PDF-fillout method, has been provided by Daniel Walker. You can download it from git hub at Your feedback us greatly appreciated on any of these methods.

We are interested in learning how the new GUI and the overall tax programs are working for you. Please take a few minutes to answer our Anonymous OTS User Survey. Your feedback will help in improving OTS.

In the USA this year, Federal Taxes are to be post-marked, on or before, Monday, April 18, 2016. Most State Taxes are due that day as well, or later.

You can also check the OTS Blog for status updates.   All -updates, -notifications of issues, and -contributions of additional forms, from you, the users, are always much appreciated!     Special thanks again to all contributors.

Also, as the New Year starts, remember that the Payroll Withholding Calculator is helpful for calculating adjustments to your weekly pay-check deductions throughout the year, to avoid under-withholding or over-withholding.


The OTS tax package is intended to be used with the Tax booklets published by your government for determining what numbers you need to enter, and then it assists you in doing the otherwise tedious calculations while showing the intermediate and final numbers. It takes care of the tedious and error-prone work, leaving you with just the simple task of copying the answers to your final tax form. OTS is particularly useful in combination with the Adobe PDF Fill-In forms distributed by the government agencies. (This avoids the otherwise costly problem of producing official updated output forms, -- one of the major downfalls of prior open-source tax efforts.)

The core of OTS is a set of straight-forward text-processing programs. The OTS_GUI is the default Graphical User Interface. The GUI allows you to conveniently enter tax data, and then invokes the appropriate text program when you press the Compute button. Alternatively, you can directly enter your tax data by editing the text files with your favorite text editor, and then process it by invoking the appropriate tax-solver program. Many people now days use the GUI, so that is the default mode according to instructions in the package. Since the GUI is fairly self-explanatory itself, the detailed documentation sections below focus on how the core text programs work, for those interested.

Example screen shots of OTS_GUI.

Although originally created for US 1040 tax forms, the routines have also been used to solve other tax forms, and for other countries or states. Some error checking is included.

While the OTS programs developed over the past fifteen years, results have often been checked against commercial packages. The answers produced by OTS have matched to within a dollar or so, differing sometimes by rounding effects. Certainly your mileage may vary. Always double-check your tax forms!!


Download OpenTaxSolver

OpenTaxSolver for the last year's taxes (2014 Tax Year) (and previous years) can be downloaded from:
        Download OpenTaxSolver - 2014 OTS Download-Page

Both source code and compiled executables are available for download. Example form-data files are included. Typical package size is about 0.5 MB (fairly small).

Packages for Linux/Unix/MaxOSx are tar-gzip (.tgz), while packages for Microsoft are zip files. To unpack,   tar xfz package.tgz   or   unzip . Will unpack into a directory of the same name. (To see contents prior to unpacking, tar tfz package.tgz   or   unzip -l .)

Tar packages contain precompiled executables for Linux (32-bit and 64-bit), and MacOSx.
Zip packages contain precompiled executables for Microsoft PCs.
Source code and compilation instructions are also provided in all versions.
(Uninstall by simply deleting files in the directory. No registry entries are made.)

Other Links

Feedback welcome.

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Aston Roberts -