P.S. sorry, this ended up being a long post... but some things needed clarification before opinions sway people.
Not sure I read your tone right.
The rules for taxes, and residency status are applied across almost any country in the world.
We are lucky that Spain has "Double Taxation" agreements with most developed countries across the world.
This means, If you pay your annual income tax to Spain as your primary tax residency, then the amount you have paid will be counted towards whatever you have to pay elsewhere if an agreement exists.
Example time
You earn 10,000€ in 2025 and you spend more than 183 days of the year in Spain (it becomes primary tax residency)
You then need to file your annual tax return in Spain first.
Spain has tax rate of 20% and thus you pay them €2000
You also spent 90 days in France in 2025, so you do a tax return there.
France has a tax rate of 19.5% - which would equal €1950, but you have already paid 2000 to spain, and therefore nothing is due to France.
You spent 90 days in the UK, where you have properties and other assets, so you do a tax return there.
UK has a tax rate of 20.5% - which equals €2050, you have already paid Spain €2000 leaving €50 due to Her Majesties Revenue Collectors 
p.s. if income is taxed at source (e.g. UK pension or other income) then it is calculated in spain as X amount of tax already paid on it and thus not due.
This is a very simplified version...
The internationally accepted norm is:
If you spend more than 183 days per year in any country, then that country will become your
primary tax residency.
Any other country that you spend any amount of time in, and earn
Money whilst you are there, has the right to charge you tax on either: 1. The income you earned there - 2. Your worldwide income.
Even now, working remotely (Office work but sat in front of a laptop) is classed as working in the country, and thus taxes are due to that country (Germany has special plans to enforce this).
But if you spend less than 183 days per year in a country, the place you spend the most amount of time will become your primary tax residency.
Quote:Pay your global taxes to Spain then they are hardly going to mind you spending whatever time you want outside the country, the longer the better as far as they are concerned.
This is actually incorrect... They will want you to spend all your hard earned
Money on their local economy, not take it abroad and spend it elsewhere.
There are many special tax rules, writeoffs, and classifications that actually encourage local people to spend locally. The tax
Money is all great and well, but the real impact comes when they can charge taxes on the already taxed monies
Another Example...
You earn 10000, pay 2000 tax.
Then you spend the remaining 8000 over the year... of which about 525 is sales tax of about 7% (total tax 2525 paid)
The business who you bought from needs to pay 20% on profit... so we'll say 30% margin on all goods = approx €450
The total amount of your Money that went to the tax office ends up being about 3000, or 30% vs the original 20%... 30% of raw tax...
The % amounts here are random numbers to simplify the math...
But I once calculated when I was in Germany, I was only truly seeing about 30 odd cents of every single Euro earned as a business owner... the rest was taxes in some way or another.
Just be thankful that we are not US Citizens who are taxed on worldwide income as long as they have citizenship... even if they have lived out of the country for 10+ years... and there is always some amount due to them as their double taxation treaties do not cover the full scope of income.
ALL international banks are forced to report their US Citizen customer accounts to the US treasury so the US can claim taxes on any and all movements.
There is a special sign up process for US Citizens with banks.
Only way to get out of it is to give up citizenship...
I hope the UK does not follow this.