Are you a Spanish tax-resident for tax purposes
If you are currently living in Spain, you would assume that you would also be a Spanish tax resident. That is not always the case. The underlining rule is that if you live more that 183 days of the calendar year in Spain then you are deemed to be tax resident also. Although this is usually the deciding factor there are exemptions to the rule. If the ‘centre of your interests’ is arguably in the United Kingdom, Her Majesty’s Revenue and Customs (HMRC) could reason that you are responsible for tax there, not Spain.
Where is your ‘centre of interests’? Well, you could quite conceivably spend most of your time in Spain whilst still having a house in the UK, a business or job based in the UK, children in school in the UK and/or a spouse in the UK. If all these were the case then you would almost certainly be UK resident for tax purposes. You would also be liable to tax in Spain (in theory) if you spend more than 183 days here. In practice there is however a ‘double tax treaty’ in existence between the UK and Spain which ensures you do not have to pay tax twice as a result.
If you currently reside in Spain and the majority of your ‘centre’s of interest’ are (in Spain) then you will be deemed as a tax resident by the Hacienda (the Spanish tax authorities) and liable to pay taxes on your assets world-wide.