If you are a non-resident property owner in Spain, the annual Modelo 210 non resident property tax must be paid before the end of this month.
The most economical way to have this tax calculated and paid on your behalf is through Taxes on Line, a company based here in Lanzarote, but that deals with this tax for people who own property all over Spain.
You can get full details of their service and even calculate the tax due at their website: Taxes On Line