VAT reduction during house construction

Crazy. We put so much effort into every single day we could get earlier. And now the building inspection is probably scheduled about 10 days before 1st July. Our contract also states that the prices in the billing will be adjusted accordingly if the VAT changes before handover. Let's see what can still be done.

Correct. But then individual services would have to be agreed upon and interim acceptances between the customer and the general contractor would have to take place.
However, there would probably also be different limitation periods for the warranties.

In my opinion, acceptances do not have to take place for that, but I would have to look it up again in the UStAE. Rather, there must be a logical division; there are quite clear criteria for that, and it must be invoiced separately. In our case: We receive an invoice for an amount x (15% of the net price) after the completion of the foundation slab – this is a classic partial service. The VAT for this arises with the end of the tax assessment period after execution of this partial service.

Edit: Should an acceptance actually be necessary: We are talking about half a year here. So if I have to accept the foundation slab in order to pay 3% less for it – logically, I accept the part.

Rather, it must be a logical division, there are quite clear criteria for that, and it must be billed separately. In our case: We receive an invoice for an amount x (15% of the net price) after completion of the foundation slab – that is a classic partial service.

But as soon as the invoice contains the word down payment, advance payment, or similar, it is no longer a rendered partial service, even if part of the work has been carried out, right?

But as soon as the invoice contains the word Akonto, advance payment or similar, it is no longer a partial service, even if part of the work was carried out, right?

In principle, you can also call a partial service a teddy bear; it remains a partial service as long as it relates to a specific performance and is invoiced separately (if applicable, accepted).

billed separately

Yes, but exactly that is always super vague. When is it a separate invoice and when is it not? From my naive understanding, separate invoices should not have any references to each other, which can no longer be the case due to words like "advance payment" etc. It gets even vaguer when invoices have not been properly issued by the craftsman. For example, I received a first invoice for scaffolding, without the word advance payment or anything else that would suggest further work on the roof. But the second invoice suddenly refers to the first invoice as an advance payment. Is that now separate or not?

Yes, but exactly that is always so vague. When is it a separate billing and when is it not? From my naive understanding, separate invoices should have no references to each other, which can no longer be the case with words like "advance payment," etc.
It gets even vaguer when invoices are not properly issued by the craftsman. For example, I received a 1st invoice for scaffolding without the word advance payment or anything else that would suggest further work on the roof. But the 2nd invoice suddenly references the 1st invoice as an installment payment. So is that separate or not?

Well, what service does the 2nd invoice correspond to?
Is it an economically separable, separate service or is it simply a progress payment without a concrete reference?