Most visitors to Indonesia may obtain a visa on arrival to Indonesia, unless they are a citizen of one of the visa-exempt countries. However, some countries must obtain a visa in advance from one of the Indonesian diplomatic missions before being allowed to enter Indonesia. All visitors must hold a passport valid for 6 months as well as a valid return ticket. Passport with validity of more than 3 months can be accepted in special cases or business travel. The immigration officer at the port of entry may ask the passenger to produce any necessary documents (such as hotel reservation and proof of finance).