This is a really general question but does anyone have an idea of the annual property tax due on a small casa de campo ( 55 sq mtrs ) with 1.5 hectares of land within the Tortosa ajuntament area and also the interest/penalties due for non payment for a few years.

The bill will depend on the official classification.  I think there is a limit as to how far they can back track on unpaid taxes which is 5 years???

Do you not get notifications of payments due from BASE ?

I haven't had anything. It's a small country house, used as a holiday home so no postal delivery and have had no notification by email either. Just looking to know the answer before I ask the question " officially ".

Sounds like it might be a good idea to visit the BASE office in Tortosa with all your paperwork.  Might be an idea to have a word with the estate agent that sold you the property first.

I used to have similar size property & land in Coll de l'Alba & paid 30€ per year rustic tax, go to BASE or forget it as most do.

If and when you pay your taxes to Base, you will be charged back tax for the last four years, and will be calculated at an increased rate, so could be around double of what you expect to pay.