EHP is a document, that the Dutch tax office requests to declare your income which is not taxed in the Netherlands. This means, that you have to confirm that you had or had not income in other country (such as in your home country).
Do you work in Austria and are unable to grasp their tax system? Should you file a tax return? How would you do it? What do you need for it?
If you are employed in Austria chances are that you are entitled to a tax refund. What documents do you need for that?