I'm arriving to Barcelona at midnight and would like to take a cab since the night transport is not too convenient. I know that taxis at airport stands can be prone to scamming tourists and it's not recommended to use them in some cities, e.g. Prague.
Unfortunately Uber is unavailable in Barcelona, so what's a reliable way of getting a taxi from the airport without getting ripped off?
I live in Barcelona and I have taken a taxi from the airport lots of times. Taxi system is a very regulated sector in Barcelona. Fares of official regular taxis are controlled by the IMET, the Metropolitan Taxi Institute which depends from AMB (Barcelona Metropolitan Area). Specially at the airport, you won't find a "cheapest way" to take taxi, you will find taxi fares that are the same for all taxis.
You will have to pay a supplement of 3.10€ for catching a taxi from the airport and 1.00€ for each piece of luggage placed in the boot. When you get to the cab, a rate called "la baixada de bandera" is applied. Then there is a fixed rate for distance covered and also a fixed rate for the time passing when the taxi is stopped: you will see how these are being charged on the taximeter located inside the cab. Note that these rates are more expensive on weekends and holidays and also from 20:00 to 8:00 than at the rest of the day. At the end of the journey, the above mentioned supplements will be added to the taximeter. Notice that a minimum fare of 20.00€ (including supplements) will be always charged to you for the fact of getting a taxi at the airport.
You can find official information about taxi fares from the IMET at this website (in Catalan).
Taxi sector is so strictly regulated nowadays that I think it's very difficult you get scammed. As you can see in the pictures of the official website of IMET, you will find the driver identification and the taxi license number located very visibly at the interior of the cab. Anyway, if you need to make a complaint, you can always ask for a receipt to the taxi driver. Such a receipt will contain all the relevant data you need to fill out the official complaint form that you will have to send along with your receipt to the following address: Institut Metropolità del Taxi, carrer 62 núm. 18 - Zona Franca - 08040 Barcelona.
You can find some more practical information about Barcelona airport taxi service at this website (however note that it's unofficial).
The cheapest way to take a taxi, is not from the airport (which include the fees someone already mentioned).
Happen that just 1 week ago I had a friend who came at midnight too, so I know pretty much what would be the safer/cheapest way.
Your best shot is to take the Aerobus, that goes from the Airport T1/T2 to Catalunya square (center of the city) and cost 5.90€ (way chepear than a cab).
Then you can take a taxi (there are many around) and avoid airport fees (will be still lots cheaper).
I higly recommend you to do this, since it's very safe to take the bus (the only problem could be your arriving time, but if you hurry you may still get it
Ps: Something to keep in mind on Aerobus.
Ps2: If you think the bus is not an option, then you are at your own with taxis. Except if you want to sleep in the airport until 5 am (when the metro opens) or if you come on saturday when the metrol is open all night.
It really depends on the time you are arriving.
As others have already mentioned, you can use Aerobús to get to the city center. The last one is at 1.05, as they say in Timetable:
From 05:35 h to 07:20 h every 10 min
From 07:30 h to 22:20 h every 5 min
From 22:25 h to 01:05 h every 10 min
You mention
since the night transport is not too convenient
Well, it really depends on what convenient means to you: Aerobús is quite fast and goes straight. And all the options are safe: I have never heard about any safety problem in any of them.
Then, you can use a Night bus all night long. It is important to mention that it takes more time than Aerobús: around 40' instead of 20'. It is the number N17 and its current depart times from the Terminal T1 are:
21:55
22:05 22:15 22:25 22:45
23:05 23:25 23:45
00:05 00:25 00:45
01:05 01:25 01:45
02:05 02:25 02:45
03:05 03:25 03:45
04:05 04:25 04:45
If you really have to take a taxi, you'll find plenty of them and its fares are around 30€ at night to go to the city center.
The best way to not get scammed in pretty much every country in the world is to get a taxi with a meter, and/or ask how much it will be before you get on, so you know what to expect. The driver will know to give you at least an approximate value he should stick to.
Check online for the taxi fare ahead of time, but also consider that night-ride fair is usually more expensive.
