What if my arrival date changes after I get the approval letter?

Dear Shaun Kennedy

That is totally fine, as long as  you arrive in Vietnam on 4th April, you can use the current letter to  obtain your visa at airport. There will be no problem at all in this  case.

Please let us know if we can be of any further assistance

Best regards,

Dear Niki Corich

In case you have not confirmed your date of arrival yet, you can put the earliest arrival date on your application, and you can arrive later than the date stated on your letter, however, still need to exit before the visa expiry date

Dear Todd Field

Thank you for your inquiry.

That is fine, you can arrive in the country on 21st April with current letter. There is no problem with that.
However please be noted that you still must exit the country before 18th May. 

Hello

Thank you for contacting us. 

If your travel plan is not confirmed yet, we advise that you put on the earliest day you wish to arrive in the country, please note that you can arrive later,  NOT earlier than the date you submit on the application.

Please do not hesitate to let us know if you have any other questions.