Two Amsterdam tenants had great success in reporting their landlord to the Huurcommissie rent tribunal for charging them exorbitant rent. The Huurcommissie ordered the landlord to lower the rent for a small, leaky, drafty room on Keizersgracht from 1,950 euros to temporarily 95 euros per month. The rent for another room in the same building was lowered from 1,200 euros to temporarily 93 euros.
Mh, I don’t think this only affects deductions. Otherwise people could just waive their right do deduct costs related to the housing units discussed in the article. I don’t think this would make a huge difference, i.e. I don’t think the deductible costs are that significant.
However, if you don’t pay your janitor or your nanny properly, but provide them with cheap housing instead, you can (illegally) save a lot of money.
Anyway, that’s my guess, but I’m very open to new knowledge. :)
I looked into it a bit more and seems like we are both somewhat right: https://www.tz.de/muenchen/stadt/guenstige-jetzt-jagt-ihn-das-finanzamt-das-ist-ein-unding-preise-muenchen-vermieter-65-verlangt-zu-zr-91597287.html