Legally, since both Germany and Austria are members of the Schengen Area, there are no permanent border controls between Munich and Salzburg, and you are not typically stopped for a passport check when crossing by train or car. However, you are legally required to carry a valid passport or national ID card with you at all times when crossing international borders in Europe. In 2026, due to ongoing migration and security policies, German and Austrian authorities frequently conduct "temporary" spot checks on trains (like the Meridian or the EuroCity) and at the Autobahn border crossings. If you are a non-EU citizen and are found without your passport during one of these checks, you could face delays, fines, or even be removed from the train. Furthermore, you will need your passport to check into a hotel in Salzburg, as Austrian law requires all foreign guests to provide official identification. Even though the journey is only about 90 minutes and feels like a local commute, you are crossing a sovereign border. Therefore, you should never leave your passport in your Munich hotel; always have it in your possession for any day trip into Austria to ensure a hassle-free return.