Open-source Tax Solver (OTS)

January 7, 2017
- Project -
- Download - Last Year's Version - (for 2015 Tax Year)

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 2016 Tax Year is underway. Initial release is still expected by the end of January. As in prior years, the update is planned to 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 and checking 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.

Latest News: ... as of 1-7-2017 ...
Everything is now updated for the most recent tax-year (2016), and is undergoing testing -- except for the NY, PA, NJ, and NC State forms -- which we are still waiting to be released from those states. Hopefully they will be released this week or so, and then we will complete all updates within just a few days. Release for beta-testing will then follow immediately, followed by the stable wide release within a week.

Each year it keeps getting better. This year there are several minor improvements.

  • For forms that support Auto-PDF-Fillout, an optional set of lines has been added to supply your name and address only for the auto-fillout option. You can leave these lines blank. They do not affect any calculations. But if you fill them in, and if you select auto-fillout, it will place your name and address on the forms, so you do not have do it manually. Otherwise, you can always enter your name and address manually on the final version of your forms with your PDF viewer.
  • For the MS-Windows version, we have improved the automatic selection of your PDF viewer for the Auto-PDF-Fillout feature. This was a problem for some users last year.
  • For the Federal 1040:
    • Added a line (L8b) for entering Tax-Exempt Interest. This is only used and needed for Social Security Benefits calculations. It is not used if you are not yet receiving Social Security payments.
    • OTS now does the Social Security Benefits worksheet, for whom this applies. This had been much-requested. It now calculates the Line-20b entry for you. (Your SocSec benefits entry for Line 20 changes. Previously you entered the amount for Line 20b, which was the result from the SocSec Worksheet. Now you just enter amounts for Line 20a, which are the raw amounts from the box 5's of all your SSA-1099 and RRB-1099 forms. )
  • Help buttons have been added to the GUI. These provide information about the version of the OTS package, some brief instructions on how to use it, and links back to our web-site for additional help, information, and updates.

OTS now has two movies:

  1. 1-minute OTS Overview - Quick brief on what OTS does.
  2. OTS Introduction Video - How to download, install, and use OTS.
The first one should be good for anyone wanting to see what it does and how it works - before downloading it. The second one should be helpful for first time users.

Last year's release added a new Auto-Fillout option. It saves time by filling out many of the numbers onto the actual government PDF tax-forms. For enhanced security you enter your name, address, Soc-Sec number, and mark some check-mark items directly in your PDF-viewer. Auto-Fillout of PDF Forms is presently supported for the US Federal (1040 and related forms), as well as the PA, CA, and OH State forms. (Other states are not yet supported for auto-fillout.) If Auto-Fillout is supported, you will see the Auto-Fillout option when you click Print. This new feature may not be supported by all PDF-viewers. But it seems to work OK with several of the popular ones. Next to the Auto-Fillout button is a button to select your favorite PDF-Viewer. We have seen good results with the Chrome and IE browsers, Evince, Atril, and Xpdf viewers, as well as LibreOffice and the Safari browsers.

The version of OTS for last year (2015 Tax Year) is still available at Downloads. As in prior years, it contained programs for US 1040 with Schedules A, B, C, D, along with the 6251 (AMT) & 8949 forms. All of the Federal Forms and Schedules are generated from the main 1040 program, except for Schedule-C, which is done as a separate program in the set. The package also contained State versions for California, Pennsylvania, New Jersey, North Carolina, Ohio, Virginia, New York, and Massachusetts.

OTS FaceBook Page:    
Please like-us on our FaceBook page.

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.)

Alternate Automatic PDF Forms Fill-out:
An alternate PDF-fillout method, was provided by Daniel Walker. You can download the 2014 version from git hub at He may update it for this year. This method may require you to install additional software, but is reported to work reliably. Your feedback is appreciated on any of these methods.

We are interested in learning how OTS is working for you. Please take a few minutes to answer our Anonymous OTS User Survey. Your feedback will help in improving OTS.

The feedback received so far has been very positive. Next month we will add a page which summarizes the results.

In the USA this year, Federal Taxes are to be post-marked, on or before, Tuesday, April 18, 2017. 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 nowadays 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 last year's taxes (2015 Tax Year) (and previous years) can be downloaded from:
        Download OpenTaxSolver - 2015 OTS Download-Page

Both source code and compiled executables are available for download. Example form-data files are included. Typical package size is about 1.6 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 -