The "Visa approval letter" is a letter issued by Vietnam Immigration Department that allows you to enter and exit Vietnam for a given time period. With the approval letter, you can pick up your visa upon arrival at one of the three International Airports in Vietnam (Hanoi, Ho Chi Minh City and Da Nang).
At the airport, the corresponding authority will verify the details on the approval letter based on your passport and travel documents. As long as you make sure you input the correct details when applying, you will surely be granted entry upon arrival in Vietnam with the approval letter.
However, it is strongly advised that you read our website and follow all the instructions carefully to avoid problems or delays at the airport.
What the approval letter looks like.