Upvote:4
To answer the first part:
You need a photo ID card with a photo and a number which is recognised nationally or at the level of Europe. In the case of all Spanish nationals, this means their ID card called a DNI, or Documento Nacional de Identidad. Only if this has been lost or misplaced would a Spanish national use their passport instead. This card is used for all transactions from credit card purchases (although many shops no longer insist as most cards require PINs) to the renting or purchase of flats. The ID card also works outside Spain. My wife, for example, travels to the UK using this ID card instead of her passport.
Nationals from France, Italy, etc, use their country's ID cards when in Spain. As British nationals in Spain do not have an ID card, they usually carry their passport or a photocopy when on holiday. But in the case of UK nationals resident in Spain, they do something different: they use the new credit-card-sized photo-ID driving licence along with something called a NIE which is a number allocated to them by the government when they register as residents.
So, applied to your case, I would suggest using your driving licence and a photocopy of your passport. That should be more than enough!
To answer the second part:
I understand that hotels have to keep a list of all guests, dutifully identified. (And in Spain this naturally means the ID card.) I've stayed in places which do not do this, or which ask for cash, but I suspect this may have something to do with avoiding taxes!
Upvote:6
In addition to Ian's answer, I'd like to add a few information from law:
Firstly, is this checking of ID a legal requirements in Spain, or is it just something the hotels seem to like doing?
It is a legal requirement in Spain. Every hotel must keep a registry of guests and send a copy to the police - nowadays, the "copy" is usually an electronic communication. The hotel is also required by law to check the data in the registry with a Spanish ID or a passport. I assume that ID cards from European countries which are valid to travel to Spain without a passport can be used instead of the Spanish ID or passport.