Make sure that your Passport is valid :
Austria
Make sure that your Passport is valid
Assuming you have been following the rules of living in Austria, then your passport will, of course be valid. However, if it has lapsed, you will need a valid passport. This doesn't just apply to leaving permanently, but whenever it expires. So always make sure that you're fully aware of expiry dates and can take action in enough time to avoid expiry being a problem.
If you do find yourself with an expired passport, then you will need to contact the Foreign & Commonweath Office who can arrange for a new one. It is recommended that you allow plenty of time (according to the website at least 5 weeks).
Foreign Office - Passport