Since January, 2014, there is a flat taxi fare from or to the airport, which is 30 euros. This applies going from the airport to the M-30 loop or from the M-30 loop to the airport.  No add-ons are permitted for the taxi, such as an extra charge for luggage. When getting into a taxi, tell the driver that you will need a receipt, which many business travelers ask for. This will keep the taxi driver honest, because if the taxi driver charges more than the 30 euros, one can denounce him to the authorities and he may lose his license.  

 

This regulation has been made by the Madrid City Hall. The M-30 is a motorway that circles the central districts of Madrid.

 

Pick-ups and drop-offs outside of the M-30 will be charged a minimum of 20 Euros.

The main page for taxi fares in Madrid is the following:

www.madrid.es/
If you are unable to understand Spanish try this Google Translation
Taxis in Madrid are white with a diagonal red band on their front door bearing the emblem of the city. Available taxis have a green LIBRE sign in the windshield and a green light on top. The 'fare' number of either 1, 2 or 3 will be shown next to this light. To hail a taxi all you only need to do is to raise your hand.
There are also several taxi ranks around the city, indicated by a blue sign with a white letter ‘T’. At railway and bus stations and at the airport taxis must be taken from the corresponding ranks. Throughout the rest of the city they can easily be stopped in the street.
There are more than 15,600 taxis in Madrid, so it is not usually difficult to find one available in the city’s main thoroughfares. Journeys are usually paid for in cash, and most of the taxis in Madrid do not accept credit cards, and they only carry change for payments up to €50.
 
FARES
The above  taxi fares have been in force since DEC; 2012: 
 
 
EXTRA CHARGES
There are some extra charges for uptodate information please read the above website.
 
CUSTOMER'S RIGHTS
Ask for a receipt (in Spanish "un recibo por favor") if you feel the charge is too high - the driver is obligated to give you one showing NIF (tax code), amount, date, licence number, plate, or a printed receipt.
Choice of route.
Change for payment up to €20.
Air conditioning in the summer.
Adjustment of radio volume.
A zero fare will be applied in case of incidents, and on return journeys to the perimeter area.
VAT is include in all fares.
Ask for a receipt (in Spanish "un recibo por favor") if you feel the charge is too high - the driver is obligated to give you one showing NIF (tax code), amount, date, licence number, plate, or a printed receipt.
LOST AND FOUND
Office at Paseo del Molino 7. Subway: Legazpi. Phone: 915 279 590
 
RADIO TAXIS
There are several private companies that can be called to order a taxi. You should bear in mind that in these cases the taxi meter starts running at the point where the taxi driver is when (s)he picks up the call.
Radio Teléfono Taxi / Euro Taxi (adapted for disabled persons): (+34) 91 547 82 00 / (+34) 91 547 85 00 / (+34) 91 547 86 00
Radio-Taxi Asociación Gremial: (+34) 91 447 51 80 / (+34) 91 447 32 32
Radio-Taxi Independiente: (+34) 91 405 12 13 / (+34) 91 405 55 00
Teletaxi: (+34) 91 371 21 31 / (+34) 91 371 37 11 / (+34) 630 907 990