I am going to apply an approval letter to visit Vietnam. However, I have not known exactly the date I would enter Vietnam yet. Does the approval letter have any validity date? Can I apply it first and then change the arrival date later?

The approval letter is the official letter which allows you to enter Vietnam and get visa on arrival. This letter indicates the entry date and the exit day clearly. The length of your stay in Vietnam is also showed in this approval letter. You can enter Vietnam at the entry date or later than the entry date and leave Vietnam some days before the exit date or at the exit date.

For example, you can see the approval letter in the picture. The applicant in this letter is approved to get visa to enter Vietnam from 26/6/2019 to 26/7/2019. He can enter Vietnam at 26/6, 27/6, 28/6 or even 26/7, but he have to leave the country before 26/7 or at 26/7.

At the airport, the officers will follow the approval letter and make the visa stamp. Therefore, the approval letter as well as the visa stamp has the validity date. If you are going to stay longer, you can consider to make the visa extension or renew your visa.