LEGAL REQUIREMENTS IN SPAIN..

[Tranona]

If the owner is not resident the boat should be registered on the Spanish register after 18 months which a change of 12½% ( I think)but can keep the UK flag and registration...of course he can exit and re enter to reset the clock.

EDIT although I have just read on Google that f the owner is not resident the boat can stay no taxable unlimited time....bit confusing..maybe

Not confusing at all. The 12% applies to those becoming resident and applies to assets other than boats. It can be reduced by declaring all assets on taking up residence. Completely different from EU rules on Temporary admission. Hundreds, if not thousands of boats owned by non EU residents kept in Spain (and other EU states) under temporary admission. The OP explains how he maintains this - by going to Gibraltar with the boat which is sufficient to restart the clock. This is unlikely to change even if there is a deal on Schengen access with Gibraltar as it will still be outside the single market and EU customs zone.

 

[wallacebob]

This new thread may be of interest: Royal decree 339/2021
Seems to imply any boat kept permanently at a Spanish marina must comply with Spanish regs. eg inspection every 2 (?) years, life vests, flares, etc. I am unsure; does this mean Spanish registry too, to ensure Guardia are able to check on you and the scheme to be administered.

 

[Tranona]

This new thread may be of interest: Royal decree 339/2021
Seems to imply any boat kept permanently at a Spanish marina must comply with Spanish regs. eg inspection every 2 (?) years, life vests, flares, etc. I am unsure; does this mean Spanish registry too, to ensure Guardia are able to check on you and the scheme to be administered.

Leaving aside the equipment issue (which does not appear to apply to private boats) it is well established that non residents do not need to register in Spain and that those who have taken up residence bringing their boats with them and paying the 12% matriculation tax can keep their UK registration.

Having said that Spain is entitled to make that condition as Portugal did a few years ago. However their rules were very specific and both easy to comply with (just equipment) and relatively easy to avoid by leaving Portuguese waters every 6 months.