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Tax-Calculator simulates the US federal individual income tax system. In conjunction with micro data that represent the US population and a set of behavioral assumptions, Tax-Calculator can be used to conduct revenue scoring and distributional analyses of tax policies. Tax-Calculator is written in Python, an interpreted language that can execute on Windows, Mac, or Linux.
Results will change as the underlying models improve. A fundamental reason for adopting open source methods in this project is so that people from all backgrounds can contribute to the models that our society uses to assess economic policy; when community-contributed improvements are incorporated, the model will produce different results.
There are two common ways to get started with Tax-Calculator:
The first way is to install the Tax-Calculator repository on your computer. Do this by following the instructions in our [Contributor Guide](http://taxcalc.readthedocs.io/en/latest/contributor_guide.html). After the installation you can read the source code and either use Tax-Calculator as is or develop new Tax-Calculator capabilities.
When using Tax-Calculator on your computer you will have to supply your own input data on tax filing units because the repository does not include a representative sample of tax filing units. However, you can use it to estimate tax liabilities and marginal tax rates for any collection of filing units specified in [Internet-TAXSIM input format](http://users.nber.org/~taxsim/taxsim-calc9/) using the simtax.py command-line interface to Tax-Calculator. And you can also process your own CSV-formatted data using the inctax.py command-line interface to Tax-Calculator, but when doing this be sure to read the [data-preparation guidelines](DATAPREP.md).
When developing new Tax-Calculator capabilities be sure to read about our [coding style](CODING.md) and [testing procedures](TESTING.md) after you have read completely the [Contributor Guide](http://taxcalc.readthedocs.io/en/latest/contributor_guide.html).
The second way is to access Tax-Calculator through our web application, [TaxBrain](http://www.ospc.org/taxbrain). This way allows you to generate aggregate and distributional tax reform estimates using a nationally representative sample of tax filing units that is not part of the Tax-Calculator repository.
And, of course, you can get started with Tax-Calculator both ways.