As discussed in the tax section of the site - for those wishing to escape the UK tax man I can confirm that you can take your completed form FD9 - Spain-Individual (download from http://www.hmrc.gov.uk  search for FD9) to a Spanish tax office, in my case Orihuela and go to room 64/65 ask for Carlos he will authorise your form, assuming you qualify,  which can then to sent to the UK (details on the form) They will process it and, if they are happy, issue you a code of NT (No Tax)

How do you qualify? - well you need to be a resident, have NIE, own or rent a property, and on the padron. As usual take all of your papers plus copies. I have just taken a friend and the only thing Carlos asked for was the NIE original. However take everything including utility bills because other offices may wish to see more documents.

Then you can involve yourself with the delights of the Spanish tax system!

This is obviously for the Brits - sorry I dont know the system for other countries who have the Relief from double taxation treaty agreement and of course some dont!