To enter Tibet from Nepal, travelers will need two main documents: a Tibet Travel Permit and a China Group Visa. These documents are specific to the political and geographical context of Tibet and have distinct roles in facilitating entry.

1. Issued in Kathmandu:
   Unlike other entry points into China, travelers to enter Tibet from Nepal need to obtain a China Group Visa, which is different from the standard Chinese visa. This visa can only be obtained through the Chinese Embassy in Kathmandu.

2. What is a China Group Visa?
   The China Group Visa allows entry not just to Tibet but also to other parts of China. It is issued on a separate sheet of paper, not stamped in your passport, and applies to groups of two or more travelers. All group members must enter and exit China together.

3. Application Process:
   Your travel agency in Tibet will arrange for the China Group Visa application in Kathmandu. You should arrive in Nepal a few days before your planned departure to Tibet to allow time for processing. Typically, you’ll need to provide a completed application form, your original passport, and passport-sized photos.

4. Duration and Cost:
   Processing can take 2 to 4 business days, with possible express services available at additional costs. Fees can vary based on nationality and processing speed.

1. Required for Entry:
   The Tibet Travel Permit is mandatory for all foreign travelers to enter Tibet from Nepal, regardless of the point of entry. This is issued by the Tibet Tourism Bureau and typically handled by your travel agency.

2. Application Process:
   Your tour operator will arrange this permit on your behalf, as individual applications are not accepted. This is generally included in your tour package. For this, you must send a passport copy and details of your travel itinerary to your agency several weeks in advance.

3. Role of Your Agency:
   The travel agency not only secures your Tibet Travel Permit but also arranges all necessary trekking or special permits depending on your itinerary in Tibet. However, it is impossible to attain Tibet permit without tour booking with Tibet local travel agency.

• Tour Booking Requirements:
  Travel from Nepal to Tibet requires booking a tour with a registered travel agency in Lhasa, as independent travel is not permitted for foreign visitors. The agency will handle all permits and logistical arrangements.
• Travel Timelines:
  It is advised to plan your trip and submit necessary documents well in advance, as acquiring all permits and visas can be time-consuming.
• Current Regulations:
  Travel regulations and requirements can change based on political or environmental factors, so stay updated through your travel agency and official resources.

You can also refer to Tibet CN for regarded information how to enter Tibet from Nepal for more precised info.