There are four the necessary documents for foreign travelers who want travel to Tibet. The passport of course and the Chinese visa, which you can request at the Chinese Embassy in your country or to the Chinese Consulate. To obtain the latter, you must show the return flight ticket and the declaration of an overnight stay in China, even just one night is enough. It also serves the permit for foreigners when they are going to travel to Tibet closed zones, which you can get after arriving in Tibet, the other is the military permit, which you must obtain if you are planning a trip to some sensitive military areas: Ngari, Nyingchi and Nagqu. This permit is issued by the Military Office in Lhasa and a passport and Tibet entry permit is required to apply for it. Generally it takes 1-2 business days.
All individuals who come into Tibet must have a valid passport for at least six months. If you enter Tibet from China, your Chinese visa will be valid but only for travelers with tourist, non-commercial, resident or student visas. If you enter Tibet from Nepal, either by car from the Friendship Highway or by an international flight, it is separate visa required valid issued by the Chinese Embassy in Kathmandu, it generally takes two business days to get it.
The entry permit for Tibet, also known as the Tibet Tourism Bureau (TTB) is a necessary permit for entry to Lhasa or other parts of the Tibetan Autonomous Region and is issued to limit the number of foreign tourists traveling to Tibet.
