Since the question has arisen over the passport theft post earlier today, it’s worth mentioning once again that we have to carry an original ID document with us at all times.
Spain’s Citizen Security law (aka the gag law) does not require this to be a passport: it allows for the ID to be an EU driver’s photo licence instead. Spanish police say, however, that although this is the case as far as they are concerned, private businesses or non-police legal entities, e.g. banks, may impose other requirements … i.e. they may demand a passport.
Obviously many people worry about their passport being lost or stolen if they’re carrying it about even if they’re not hiring a car, and the easiest solution is for people to go to a notary and ask for a notarized copy. This is a photocopy made by the notary himself, on notarized paper, and with a notarial stamp and seal on it. It is therefore not a “copy” as such, but becomes an “original” passport as far as Spain is concerned.
A notarized copy will cost a few Euros and avoids the need to carry the original booklet passport. This will satisfy the police, Tráfico, banks, and anyone else who might need to see ID. For this and other “getting it right” questions, just see THIS page.