Has anybody else had a letter from BASE in Tortosa setting out details of new law for taxes based on building size. Apparently it was passed years ago but is only now being enforced. They have basically tripled our taxes and are asking for the last four years arrears with three days to pay. They have photos of our property and have estimated our square footage from these.

Last year our friends sold their house in the campo.
They had been to Base several times, over several years, to try and sort out taxes with them.
In the end, when the house sale went through they had to pay, four years taxes.

They shouldn't need to estimate the size of your house.  It should be declared in the deeds.

But what about any extra building work/extension that has gone on at any property since purchasing it, and without permission.
Then that wouldn't show in the escitura?
Base update records and photos often, so then surely they are able to assess what is owed to them.