The man page for taxi fares in Madrid is teh 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