Usually owners of Spanish properties confuse the “Spanish Tax Residence”, with the “Spanish Residence”.
In other words, people think that the «Spanish Residence Card, or «Residence Certificate» obtained in the Spanish National Police, is enough to demonstrate that they are «Spanish Residents for Taxes», and, unfortunately, this is not the case.
The “Spanish Residence Card” (or “Spanish Residence Certification“), is not the valid document to change your Tax consideration as «Tax Resident».
The Spanish Residence Card (or Certificate) only serves to declare that you are “living” in Spain, in order to facilitate the Police to have a better control over the residents in a determinate area.
In order to become Spanish resident for taxes, and then start to pay your Taxes in Spain as a normal Spanish citizen, you must obtain the SPANISH RESIDENT TAX CERTIFICATION issued by the Spanish Tax Office or Spanish Customs, and then you will start to pay your taxes in Spain, and not in your country of origin.
And, also, once you need to declare to the Tax of office from your country that you are Spanish Tax Resident, and that you do not wish to continue as Tax Residence on your country-
So, please, check with your tax adviser the taxes that you are currently paying because, even if you are not Spanish Resident, you should be declaring and paying the INCOME TAX NON RESIDENTS.