Spain has a tax implications if you are an official resident or a non resident homeowner.
Taxes in Spain are numbered and called ‘models’
As an official resident in Spain you will need to make a model 720 tax declaration in the following June of when you became resident.
This is to declare all assets and incomes abroad, outside of Spain as a ‘fiscal resident’ these assets are taxable by Spain.
As a non resident of Spain with as a Spanish property owner, you will need to make a model 210 tax declaration annually for property taxes and to show any profits you have made from the property, such as rental income.