The "recognized religions" in Austria for tax purposes are (according to Wikipedia): the Roman Catholic Church, the Protestant churches (Lutheran and Presbyterian, called "Augsburger" and "Helvetic" confessions), Islamic community, Old Catholic Church, Jewish community, Eastern Orthodox Church (Russian, Greek, Serbian, Romanian, and Bulgarian), Church of Jesus Christ of Latter-day Saints (Mormons), New Apostolic Church, Syrian Orthodox Church, Armenian Apostolic Church, Methodist Church of Austria, Buddhist community, and Coptic Orthodox Church.
Taxpayers presumably check a box on their return for one of those 13 groups, or "none of the above".
There are a lot of Evangelical churches springing up around Europe that are not recognized by the government. Known as Freie Gemeinde in the Germanic countries, these churches are growing rapidly and since they are not recognized they recieve NO taxpayer support.