Posted: Sun Feb 27, 2022 8:44pm
https://www.icalculator.info/spain.html
The above is a link to a tax calculator. Use the advanced button in order to input your age. This can give you, if properly used, a good guide to the amount of calendar year tax you are liable for. Usually April/May is a good period to complete your tax return via an accountant. Up to €120 per annum for an uncomplicated return is normal.
ALL income must be declared to Hacienda/Tributaria, if you spend more than 180 days in Spain, and have a padron, residencia/TIE etc. In order to avoid HMRC double taxation at the very least you will need a fiscal residency certificate to present to UK tax authority. This may take many months to process. In Spain you have to declare any Govt/forces, eg blue light service pension even if taxed at source AFTER being Spanish tax resident. Not declaring this may attract a Hacienda fine until resolved. You will not pay double tax, but the income might put you into a separate income bracket. The entire process can be less stressful if using a tax advisor (capable of doing both UK/Spain documentation). Somebody like Indalo partners in Mojacar can do that, as can many other competent accountants in the area.