For the gross / net calculation of salaries and the income tax calculation of self employed persons as well as the calculation of the church membership contribution, please use the following links:
Gross / net calculation of salaries
Income tax calculation of self employed persons
Church membership contribution
With the link below you will get to the homepage of the City of Vienna. On this page you can check the conditions for a trade license, what kind of documents are necessary as well as acquire the information about the responsible authorities and the costs involved. And finally you can register for your trade license online.