Posted: Fri Jan 19, 2024 2:21pm
If you intend to become a permanent resident (and therefore a tax resident) of Spain, you will need to submit a tax return for your first year of tax residency at least, so you will be registed on the system.
On this return, you will need to declare all your worldwide income, including pensions. There are various tax allowances in place, so if you only have a small income, it is unlikely you will be liable for any tax.
Don't forget being on the tax system is important because it affects other things too, like your entitlement to free pharmacy prescriptions.