if you are a resident in dubai, you can buy your visa at the doha airport. The visa cost QR55 if paid in cash, I think if its through credit card it cost QR100, but I'm not sure, coz i only pay through e-cash. So before going to the passport control there's a counter for getting the e-cash card which cost QR75, which you can use everytime you visit qatar. The visa you buy at the airport is valid for 2 weeks. But first inquire if you are eligible to acquire a visa from the airport, as I heard that, that depends on the status or profession of the visitor.

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