4 years after construction, the office also demands land acquisition tax on the house

Here is the TE again.

I have now understood that
a) the chances of arguing here NO linked transaction are very poor
b) the VAT/sales tax must be paid

What is still unclear to me:
do I now have to pay real estate transfer tax on the VAT/sales tax as well or only on the net amount?

What is still unclear to me: do I now have to pay real estate transfer tax on the VAT/sales tax as well, or only on the net amount?

Does anyone have experience with this? Maybe someone for whom exactly such a tied transaction was identified...

Here is our excerpt with tied transaction. I have adjusted the names and the amount. It included VAT for us.

Explanations on the tax assessment
The subject of the purchase transaction is a (future) developed property. For the calculation of the real estate transfer tax, all additional amounts paid or to be paid to the seller and others, in addition to the purchase price of the property, are added to acquire the property in its (future) developed state. The payment to GU GmbH in the amount of xxx.xxx € is to be included in the calculation of the real estate transfer tax.

Why the contract for the house construction is now included in the notarized real estate purchase contract is beyond me.

I can handle that through a completely ordinary private law purchase agreement. The effort only serves as security for the general contractor so that the buyer does not work with another company. On top of the high purchase price, this also results in a huge amount of property transfer tax. That is money thrown away.

I would not have agreed to such a binding contract and would not have left everything to a general contractor anyway.

Why the contract for the house construction is now included in the notarized land purchase contract is beyond me.

Because you did not understand the context.

I would not have agreed to such a restrictive contract at all and would not have left everything to a general contractor anyway.

Smart aleck. Neither would I, but then the seller would not have agreed to the TE as a buyer.

I can handle that with a completely normal private law purchase contract. The effort only serves as security for the general contractor so that the buyer does not work with another company. That adds a huge amount of property transfer tax on top of the high purchase price. That is money thrown away.

What was handled here was a land purchase contract between the seller and the TE. This is primarily a contract requiring notarization. To fix a side agreement "extrajudicially" to it is, I think not only to me, nonsense. The general contractor wanted no security here at all; he was not involved in this clause. It was the seller who wanted to avoid bringing a lone wolf on board whose horizon ends at the common border like those of Goalkeeper’s middle house owner and neo-middle house owner. He merely applied a not necessary and therefore inappropriate means for this otherwise legitimate interest. What would have sufficed I have already stated: that the TE had submitted to a joint planning. With this he—though probably not with malicious intent—caused the TE a financial loss, yes. Money thrown away, out of stupidity, but this wound also burns without additional salt sprinkled in.

Our construction company also had something like that planned with us. Our plot of land was from Company A, we had to build and plan with Company B, and Company C carried out the shell construction. However, all companies were connected, though not entirely obvious. We were then supposed to buy the plot of land in the usual way via notarial purchase contract and then the construction via a contract for work. We insisted on paying real estate transfer tax for both.