Temporary VAT reduction by 3% until 31.12.2020

To my understanding (layman's warning), they are all wrong and moreover not only the last payment should be subject to 16%, but since acceptance was now the final invoice, the entire invoice should be calculated at 16%, i.e. the excess VAT of the prepaid installments should be offset.

I am a bit confused right now because today we received three final invoices with 19% VAT from the shell builder, carpenter, and roofer. In our case, each company issued progress invoices, but we withheld 5% of the total amount as a security retention until acceptance. We carried out the acceptance of these three trades last week. All previous invoices throughout the year were charged with 19% VAT, so I assumed that the VAT in the final invoices received today would be adjusted accordingly. However, this is not the case with any of the three invoices; all companies also charged the remaining 5% at 19%, and there is no sign of 16% on the previous invoices.

Did I misunderstand something, or did all three companies really issue incorrect invoices?

It cannot be judged so generally. What kind of work contract is this? You awarded the trades individually (that is how it reads)? How are the contracts structured, are they possibly fixed gross price contracts? More details are needed to make any statements here.

You can't judge that so generally. What kind of contract for work is it? Did you award the trades separately (that's how it reads)? How are the contracts designed, are these possibly gross fixed price contracts? You need more details to make statements about that.

We commissioned a construction company that did the planning and subcontracted the individual trades to subs. We concluded the contract with this company. The contract only states that the price includes the statutory VAT and that a VAT increase will be charged additionally. A reduction of the VAT is not mentioned. We receive the invoices themselves from the executing companies. The planning company ultimately has nothing to do with the invoices anymore. I know from our electrician and our site manager that they will correct the invoices to 16% VAT. When I asked the planning company how the VAT is handled, I was told that "each trade handles this at its own discretion within the framework of the legal requirements."

It sounds a bit contradictory. Did you only just now have the acceptance of the individual service? The security retention or warranty retention does not necessarily mean anything, as it is sometimes only paid after the warranty period if there is no guarantee. What is stated as the performance time or place on the invoice?

It sounds a bit contradictory. Did you only just have the acceptance of the individual service? What is stated as the time and place of performance on the invoice?

Yes, we had the acceptance for these three trades last week. The progress payment invoices always only show a date of execution, for example week 20. The three invoices from yesterday all only demand the security retention. All three trades were completed in the first half of the year but were only accepted last week by us together with the site manager.

If I understand correctly, you have a hybrid between a pure general contractor and individual awarding. You make a basic contract with a house construction company, but the individual billing takes place directly between the subcontractor and the client. Something similar was also offered to me by a house construction company at the time.

If that is the case, the question is, was the acceptance between you and the site manager or also between you and the "subs"? The former suggests that the invoices are correct, the latter suggests that the invoices would need to be changed. However, we are all not familiar with the contractual arrangements.
This is definitely no longer a layperson's question suitable for a forum. Legal advice on tax issues is reserved solely for tax advisory professions.

If you cannot get the invoices changed, in my opinion, you should consult a tax advisor or a specialist lawyer for tax law. Since this probably does not involve small sums for you either, I could imagine that the additional effort might be worthwhile.