I parenthesised Residencia, as it is debatable whether `Residencia' still exists. Some say it is now just 'Registration.'
It came as a surprise to me that one is 'tax resident' as soon as they obtain the Certificate of Registration.
I have sent an email to the British Embassy requesting that they investigate the situation. It seems to me ridiculous that a visitor, who does not intend to settle in Spain, is obliged to become tax resident. If I get a meaningful reply, I will post it.
Whilst I would not suggest that a person who intends to stay for 3 months should not comply with the Spanish law, I wanted to inform them of the problems which arise by doing so. I am fairly confident that most people, like myself, did not know that was so.