This is an identity number for foreigners who register with the authorities in Spain and applicants will receive an official document with their name and number. This number must be presented for various official transactions and it is essential to have an NIE number if you wish to buy a property in Spain. Applying for the number is done via an office of the national police (Policía Nacional) and sanctioned by the Ministerio del Interior (equivalent of the Home Office). Lawyers usually assist with obtaining this number.