You can register at the local police station, but in larger cities it can also be done at the Foreigner's Office (Oficina de Extranjero). If you do live most of the year in Spain, you will be violating the law if you do not obtain a resident's card. A tourist from the EU can only stay a maximum of 180 days and there is a €300 fine if you overstay.
Becoming a permanent resident is not the same Residency for tax purposes – the latter depends on how long you spend in Spain each year. Spending more than 183 days per annum in Spain will make you a Spanish resident for tax purposes and you will have to pay Spanish Income Tax on any worldwide income.
There are several tax advantages of becoming a permanent resident in Spain. For example, permanent residents over the age of 65 years, who have owned their home for more than three years, are not subject to Spanish Capital Gains Tax. If you are under 65, the maximum tax you will be charged will be 20%(this may change!) but for non-resident it will be 35%(this may also change!).
As a resident, when you sell your property you will not have five% of the total purchase price withheld and kept by the Spanish Tax Authorities as a guarantee against any tax liabilities you may have. There are also other advantages to be taken in consideration relating to inheritance tax, wealth tax and non-resident property owner's tax.
There is another form of residency in Spain that is also mandatory for anyone living in the country for more than six months in the country. This is registering your residency in the Town Hall (ayuntamiento) in the locality of your property. You might consider this your first step to becoming integrated into Spanish life.
The Ayuntamientos have much more powers than town halls in the UK, and the Mayor of each town or village personally carries a lot of responsibility. The town halls require the inhabitants to register as they receive funds from local and central government for each citizen on the register which helps them to provide local services such as policing, maintenance, health centres and so on.
Once registered on the Padrón Municipal, you are an official member of the community and this confirms your presence in the country, which can be very useful. You will need the certificate of registration (Certificado de Empadronamiento) to buy or sell a car, register your child in school, to get married and to vote in council elections. Most importantly, this certificate is required to apply for your NIE card (tax number, without which you cannot buy a property) and for registering your residency as described at the beginning of this article.
It can take time to register with each authority, but there are a number of benefits to doing so. We would recommend speaking with a tax lawyer who can fully explain all the consequence of becoming a tax resident in Spain – and you will need to do this to buy property in Spain.