Temporary VAT reduction by 3% until 31.12.2020

My layman's opinion:

The invoice is not correct because according to the BMF instruction, for advance payments (and these are advance payments, otherwise you would have had partial acceptances), the VAT must be adjusted if the service fulfillment (i.e. final acceptance/completion) falls within the period of the reduced VAT rate. This is the case here. Because the company recoups the difference, you can be sure of that. So the invoice is not correct in this respect. The final amount, meaning the final net amount, must be taxed at 16%.

Another question is whether the company is obligated to pass the reduction on to you. There are different points on this. As formulated in the contract, etc. However, if there are no specific formulations regarding VAT and the contract was concluded before 1.3.20 (there is a specific formulation in the BMF letter that can be found online) then the contractor is obliged to pass on the reduction.

If I were you, I would write the correct amounts by hand on the invoice (this is also how an architect would do it when checking invoices) and have the bank pay and transfer only the correct total amount (calculated with 16%).

The bank should actually have nothing to say about this. Of course, it can say I pay only against invoice but if you make deductions (maybe also because of defects etc.) that is nothing for the bank to deal with.

Another question is whether the company is obliged to pass on the reduction to you. There are different points regarding this. As formulated in the contract, etc.
However, if there are no specific formulations regarding VAT and the contract was concluded before 1.3.20 (there is a specific formulation in the letter from the BMF that can be found online), then the entrepreneur is obliged to pass on the reduction.

That is interesting information. Where exactly is that stated? Our ver

This is interesting information. Where exactly is that stated? Our ver

Search engine: Mehrwertsteuersenkung Schreiben BMF

You will find it quickly. However, you have to leaf through the document a bit until you get to the right passage. I don't know it by heart.

This is interesting information. Where exactly is that stated? Our ver

§ 29 UStG

What is the situation when you have a lump sum fixed price contract that states:

"Lump sum fixed price of: x € net, y € 19% VAT, gross x+y €.
The lump sum fixed price is immutable unless explicit change options are provided in the contract."

Since the breakdown into net and 19% VAT is explicitly stated, I would assume that the reduced VAT rate must apply upon handover in the second half of the year.
However, I have heard different opinions (keyword gross price agreement).

I would ask your provider there. In general, however, I do not see a gross price agreement at X € net plus the VAT valid at that time. Rather, I would consider the net price as the basis for the flat fixed price. If the contractor sees it differently, then ask him how he would have viewed it if the VAT had suddenly been raised to 21%.