When purchasing a car in Spain there are documents required to complete the transfer of the vehicle from the previous owner to you the new owner of the vehicle.
If you are a Spanish resident:
You will need a copy of your residencia and also a copy of your passport in date, if your address is correct on your residencia then this is all you will need, if your address is not correct on your residencia ID then you will also need a Padron (which is a register in your local town hall).
If you are a non-resident of Spain:
You will need a copy of your NIE number (tax identification number in Spain) in date and also a copy of your passport in date.
Also, proof of your address either your tenancy agreement if you are renting a property or a copy of your deeds if you own your property. We can sometimes accept electricity, water or gas bills. Insurance, internet or bank statements are not valid as proof of address.
Please note that all new NIE numbers have in the bottom right hand corner a 3 month expiry date from day of issue of the NIE number, if this is your case and 3 months have passed then you will have to obtain an up to date copy of your NIE number.