Spain, a Hague Convention member since 1978, accepts apostilled UK documents as legally authentic. Spanish authorities, notaries, registries, universities, and government offices cannot independently verify UK documents. The FCDO apostille provides an official chain of authentication, avoiding the long and costly full legalization process.

Not every document needs an apostille. Only public documents issued by government authorities, courts, or notaries require one. Private letters, contracts, or internal business communications are generally excluded.