International journeys outside Germany are permitted for certain countries but generally require prior approval by Avis.
If approved by Avis, a Cross Border Fee (CBF) is payable. This amounts to Euro 5.00 per day, Euro 25.00 per week and maximum Euro 25.00 per rental.
If approval has been given, the following provisions shall apply:

What countries am I allowed to take the vehicle to?

You are only allowed to use the vehicle in the following countries: Austria, Andorra, Belgium, Switzerland, Czech Republic, Germany, Denmark, Spain, France, Finland, Liechtenstein, Great Britain, Hungary, Croatia, Italy, Ireland, Luxemburg, Monaco, Norway, Netherlands, Portugal, Poland, San Marino, Sweden, Slovakia, Slovenia.

Entries into Italy (I), Czech Republic (CZ), Croatia (HR), France (F), Hungary (H), Poland (PL), Slovakia (SK) and Slovenia (SLO) are not allowed for vehicles of car groups E, G, F, N, J and the makes Audi, BMW, Jaguar, Land Rover, Mercedes Benz and Volkswagen.
Porsche vehicles may be driven in Germany (D), Austria (A) and Switzerland (CH) only.