The NIE (Numero de Indentificacion de Extranjeros, or Foreigners Identification Number), has been, since time immemorial, a number that starts with X and ends with a control digit. IE, X1234567L. Check out Gabilos.com for a free app to generate your own.
Well… it seems that there are now so many foreigners in Spain that they have had to change the system. So NIEs now start with Y and are one digit less – the previous NIE would now be Y123456S.
Well, there are a lot of us guiris, and we are a demanding lot. Pity we are so demanding that they had to get rid of our Residencia cards (Thank you Spanish branch of the UKIP). The new bits of green paper are so much easier to carry around, together with out passport and other bits of photo id.