There are two kinds of Vietnam visa fees that you have to pay to get visa on arrival to Vietnam, including visa service fee and visa stamping fee:
1. Service fee: Visa service fee is the amount that the applicant have to pay in advance for service during a Vietnam visa online processing from receiving and checking the applicant's personal information to collecting the pre-approval visa letter from the Vietnam Immigration Department and sending it to applicant in order to get their visa stamped at the Vietnam Airports (Hanoi, HoChiMinh, Danang) when arriving.
2. Visa Stamping Fee: Visa Stamping fee is the amount that you will directly pay to Immigration Officers by USD or VND cash at the Immigration Counter to get your Vietnam Visa stamped on your passport on arrival at the Vietnam airport.