It is a legal sworn statement issued by the British Consulate, stating that you were a resident of the UK, and are now a resident of Spain. If eligible for this document then it will not be necessary to pay registration/co2 tax during the spanish car registration process.
What sort of questions will I be asked?
The main question you will be asked is the date you left the UK to come to live in Spain and the address of your previous residence in the UK.
Do I qualify for Baja Consular certificate?
If you have been living in the UK or any other country within the EU, you are entitled to move to Spain and bring your car with you as part of your personal property and qualify for an exemption of Registration/Co2 tax. To qualify you must have owned the vehicle for at least six clear months prior to coming to live in Spain and the vehicle must be in your name on the UK log book. A NIE and Padron also need to be obtained which must be less than 2 months on the day of visiting the tax office to get an exemption from paying the registration/co2 tax.
You are not permitted to sell the vehicle within one year of registering the car onto Spanish plates if using the Baja Consular. If you sell the vehicle within this time you may be required to pay the tax office in Spain (Hacienda) the co2 taxes in full.
Where do I obtain a Baja Consular?
The British Consulate in the province in which you are re-registering the vehicle in Spain.
How much does it cost?
159 euros as of June 2012.