A Spanish NIE (Número de Identificación de Extranjero) number is a tax identification number assigned to non-Spanish residents in Spain. It serves as a unique identifier for foreigners and is used for various official and legal purposes. The NIE is required for activities such as opening a bank account, buying property, signing a rental agreement, or engaging in any legal or financial transactions within Spain.

The NIE is not only for tax purposes but is also commonly used in administrative and legal processes. Foreigners, including EU citizens and non-EU citizens, typically need to obtain an NIE if they plan to stay in Spain for an extended period or engage in specific activities that require official identification.

It's important to note that the NIE is distinct from the Spanish residency status. While obtaining an NIE is often a prerequisite for residency, they are separate processes. The NIE is issued by the National Police or a foreigner's office in Spain, and the process for obtaining one may vary depending on the applicant's circumstances and the specific region in Spain.