Barrier reduction Kfw - tax confusion

Hello,

I have a somewhat complicated question. We have now bought a house. My boyfriend is employed full-time and is also a self-employed craftsman on the side. The KFW funding is not available for own labor. Now I asked the KFW how it works if the owner of the house is a self-employed craftsman. They told me that it would then be eligible for funding if he issues us an invoice. The floors all have different heights and need to be done, the entrance area as well, doors need to be widened, etc., etc., all of that falls under the funding program... Now he could issue us an invoice for €8,000 for the measures. We definitely have a real material expense of €10,000 -> that would definitely mean a loss for his tax burden -> he might get a tax refund and additionally we could apply for the funding and might possibly get 10% back? We would also legally buy the material and carry out the work. So basically everything would be super proper and fair and not cheating or anything like that, right? But somehow I wonder if that really works that way?

We would be grateful for any tips... :)

Honestly, I can't really imagine that either. At most as a UG/GmbH, but even there dangers lurk. However, if he operates as a partnership, then almost certainly not. But I'm an amateur, so: ask a tax advisor.

The logic doesn't quite make sense to me. If you have 10,000 euros in material costs – why don't you simply claim them? That would be possible without any problems. I am always in favor of saving taxes, but is this stunt worth it for a 2,000 euro loss? The subsidy for the difference also disappears. In the end, I see the problem in the fact that your friend incurs a loss within the scope of a transaction with himself, meaning he is acting for himself. If in doubt, he would have to explain to the tax office what purpose is behind it that does not serve tax evasion.