Hi SuperAggy,
my wife and I (different last names) also bought a plot of land in EB in February. We have already paid the property transfer tax 4-6 weeks ago. On Saturday, we also received exactly this letter. What did you enter? Did you provide an exact loan amount + interest + term + bank company? Do you have one large loan for the house + land, like us, or two separate ones? I sent the letter to a tax expert. He said that it probably concerns two things: 1) Detection of undeclared money 2) Construction of an immediate connection between the land purchase and house construction.
Have you received any further letters? How long ago did you fill out and send the letter?
Best regards Ronny