General knowledge:
Registration with the Padrón Municipal de Habitantes is obligatory for anyone planning to reside in Spain for more than six months per year.
To be registered is to be empadronado and when you have registered yourself, you will be given a padrón or a certificado de empadronamiento. Registering yourself is completely free and you do not need to pay to do it.
Why should you register yourself?
It’s a proof of having a valid address and not living off-the-radar or in the street.
It helps the government keep track of demographic changes and to decide how to allocate resources across regions, municipalities and communities.
You need to prove that you are not a tourist or a temporary resident if you need to open a bank account, or do anything legal.
Examples of administrative tasks that require Empadronamiento:
apply for or renew your NIE
open a bank account
buy or sell a car
get a Spanish driving license
get married
Required documents for Empadronamiento:
A valid passport and/or NIE
A house contract valid for more than 6 months with your name and NIE/passport number mentioned in it and signed by the landlord and you
Any other documents that may be necessary in your case