Performance date and payment for cellar and screed

I hope I am in the right section here. Our house is nearing completion. Now I have 2 questions. We pay everything according to the construction progress to the house construction company, according to previously agreed installments.

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At the beginning/mid-June, our basement walls and basement ceiling were poured. The invoice was issued with a service date of June even though the supports for the basement ceiling remained in place into July and a drying time of at least 28 days is assumed. [LIST=1] [*]Could one also count on acceptance of an invoice with a service date of 06/07/2020 here and could the lower VAT rate be applied? The underlying question is when concrete is considered "performed." After drying or when it comes out of the mixer? If completion is assumed after drying, then July would indeed be included. [*]Is it legitimate to remove the formwork just 16 hours after pouring the concrete for the basement walls and then place the filigree ceiling on supports 24 hours later (i.e., after 40 hours) and pour the ceiling again another 24 hours later (i.e., about 64 hours after pouring the walls)? I have not noticed any defects but I am not an expert and the house construction company apparently did not care, because they always work together with the shell builder and presumably do not criticize each other's work. I am also satisfied with the speed but of course want everything to proceed properly and I only might not see the defects because there is insulation and backfilling on the outside and plaster on the inside.
[*]Last Friday the screed was laid and the invoice for the installment arrived the very next day. Here too, the question arises when the screed counts as "performed." When it is dry or when it is installed? I mean, I cannot do any defect assessment now and have no leverage left if too large unevenness or cracks appear.

Thank you very much for your answers in advance.

1.1: good idea but drying and leaving supports in place are hardly a service. 1.2: There are so many concrete variants that this cannot be answered like that. 2: Services rendered should also be paid according to the agreement.

Basement shuttered, is set, work accomplished. Screed applied, work accomplished. Heating installed, work accomplished and not only when it is running. Defect inspection is done by your expert when he deems it appropriate. There are appointments for that. And what happened in June... that was once. Your house is nearing completion? Congratulations! Edit: why are you asking now about the basement when that was ages ago?

Edit: why are you asking now about the basement when that was ages ago?

Of course, it had already bothered me at that time. After all, basement and ceiling were quite a significant amount. But I accepted the answer from the construction company. It was similar to what was said here. Now I just had the idea to follow up on it again. But apparently, everything is correct. I had hoped it was more common that work is only considered complete when it is basically usable, and that is only the case when the things are usable and thus load-bearing and dry.

Your expert will assess defects when they see fit. There are appointments for that.

I don’t have an expert yet and know nothing about an appointment when one will inspect it. Specifically the screed. So far, I am very satisfied with everything and have always tried to inform myself about what defects can occur. But now I am getting annoyed that I did not engage and pay an expert for that. My expectation was that the construction company would keep a much closer eye on the trades. After all, in case of doubt, I will hold them accountable if it comes to the worst. But everything runs by the motto that one crow doesn’t peck out the other’s eyes. Although that sounds worse than it is. The shell construction was really a neat job (except the basement. They don’t do that themselves much anymore, and we were too late for the thin concrete walls). Only now are some things coming up here and there that I don’t like so much (actually only drywall and screed). I think that is also due to our many special requests and that we do a lot ourselves and sometimes there are coordination difficulties with the trades.

Well… I would do many things differently now. After the shell construction, I would commission the trades myself. Next house then ;)

1.2: There are so many concrete variants that this cannot be answered like that. 2: Rendered services are to be paid as agreed.

It is agreed that payment is made after completion. I have always done that and just wanted to know what counts as completion. It was concrete from a ready-mix truck ;) But it probably wasn’t quick-setting concrete or anything like that. Basically, it seems possible to remove the formwork and load it after such a short time?!