certificado de residencia

hi everyone

i have a British passport, and i intend to live in spain for a year, do i need to apply for 'certificado de residencia'(certificate of residency) on arrival?
i read many messages on the Internet, and I found confusing answers. Some say 'yes' while others say 'no'. i tried to contact the Spanish Foreign Office, but i could not find any email for it. i would like to know ahead of time so that i can prepare for it.
i appreciate your help!

thanks

nada