Posted: Wed Apr 29, 2020 8:54pm
No way to estimate your % without detailed numbers.
In general, if you receive state pension PLUS a private/company pension, you will pay more tax in Spain than in the UK.
If you apply for/are granted Residency in Spain, you can stay for more than 90 days at a time (this is the rule now, but it is widely ignored - after Brexit Transition-end, you will only be able to be in the EU for 90 days in any rolling 180 day period).
If you are in Spain for >6 months in any year, you become tax-resident (although there are some wrinkles regarding timing/reconciliation of taxes between UK and Spain).
If you are tax resident, you need to declare your world-wide wealth (property, company shares, private pension pots, savings accounts) etc. If are lucky enough to be wealthy, a tax is levied on your wealth. I think the threshold for "wealthy" is around 700k Euros, but I'm not wealthy enough to find out.