Open-source Tax Solver (OTS)

April 14, 2014
- Project -
- Download - Latest version - for 2013 tax year (Updated 2/11/2014)

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.  

The updated version of OTS for the 2013 Tax Year is released and available for downloading. As in prior years, this version contains programs for US 1040 with Schedules A, B, C, D, and with the 8829 and 8849 forms. It also contains updated State versions for California, Pennsylvania, New Jersey, North Carolina, Ohio, Virginia, New York, and Massachusetts.

The latest version contains the new Gtk-based GUI. It is called ots_gui2, because it is considered the second major version of the GUI. It basically operates like the prior one, but should be more robust, and with an improved look and feel. We may provide a compiled version of the new GUI for Mac-OS as well in the future.

An independent company is providing an add-on to OTS that automatically fills out the PDF tax return forms with the results from OTS. It is presently available for all the Federal forms covered by OTS, and one state return so far. Get it from PDF Auto-Fill-Out. They are also offering extensions to OTS that cover additional business Forms 4562, 8582, and Schedule E, for a small fee - all with the auto-fill-out feature.

We are interested in learning how the new GUI is 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, Federal Taxes are to be post-marked, on or before, Tuesday, April 15, 2014. Most States Taxes are also due that day.

To get instant email notification of new updates, click the Subscribe button under the Free(code) project page (you must have a Free(code) account to use that), or check the OTS Blog for status updates.   All updates and contributions of additional forms are 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 writing the answers on your final tax form. OTS is particularly useful in combination with the new Adobe PDF Fill-In forms distributed by an ever growing list of 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 text-program. Two optional graphical front-ends exist, OTS_GUI and OTS_tclgui-0.0. You can use OTS either by editing a text template file using your favorite text editor, and then processing it. Or, you can use the Graphical User Interface (GUI). Probably most people now days use the GUI, and that is the default mode according to instructions in the package. Since the GUI is fairly self-explanatory, the documentation sections focus on how the core text program works, 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 been checked against commercial packages such as TurboTax (Intuit), TaxCut (HR Block), and TaxAct (2nd Story Software). The answers produced by OTS have usually matched to within a dollar, differing sometimes by rounding differences. Certainly your mileage may vary. Always double-check your tax forms!


Download OpenTaxSolver

OpenTaxSolver for the current year's taxes (2013 Tax Year) (and previous years) can be downloaded from:
        Download OpenTaxSolver - 2013 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 -