Vietnam visa approval letter (or pre-approval letter) is a letter issued by Vietnam Immigration Department (a Vietnam Government Agency) allows travelers enter and exit Vietnam for a given time period. With the approval letter, traveler can pick up visa on arrival at one of international airports in Vietnam (Noi Bai airport in Hanoi; Cat Bi airport in Hai Phong City; Phu Bai airport in Hue City; Da Nang airport in Da Nang City; Cam Ranh airport in Nha Trang City; Tan Son Nhat airport in Ho Chi Minh City; Phu Quoc airport in Phu Quoc Island) or at Vietnam Embassy/Consulate.
Copy of the same document will be transmitted to Vietnam immigration checkpoints at International Airports or Vietnam Embassy/Consulate, so that when the applicant comes, the Immigration officers will have those documents on hand and will be able to issue Vietnam entry visa.
Before issuing an approval letter, the Office checks and screens visa application very strictly, so there is no case that you will be rejected at Vietnam airport or Vietnam Embassy/Consulate once you have a visa pre-approval letter in hand.
A sample of Vietnam visa approval letter that allows travelers to get visa on arrival:
A sample of Vietnam visa approval letter that allows travelers to get visa at Vietnam Embassy/Consulate abroad:
A fax document to Vietnam Embassy to confirm the Approval Letter: