How high are default interest rates?

Hello forum,

My new apartment had a few defects that the construction company also promised to fix or compensate. There is agreement about the defects ([floor heating could not be properly regulated, WC creaks when sitting down, one door is installed crookedly and only closes with difficulty and always falls fully open when it is open]). No big deal.

Unfortunately, the construction company is reluctant to provide financial compensation and is stalling with "we will discuss with the sanitary company," "it is under consultation," "we will get back to you." Actually, I had demanded the compensation by October 31. Afterwards, I even received a call from the boss saying everything was under consultation and that I would be informed soon.

But I was not. Now I have had enough. I have waited twice in trust and good faith. Since the written reminder was already sent in September, I can now also charge default interest. What is the customary interest rate for this?

What is the common interest rate for that?

I don't know how uniformly this is regulated in the EU and have little knowledge of German consumer law; in this case, it's also about Belgian (?)

The tax office in D charges, I believe, 6% p.a., I just saw on Google. Not bad, Mr. Specht, I say to that. Maybe I'll try it with the 6%. Whether that corresponds to Belgian law, I don't know. I just assume that the differences are not that huge.

The tax office in Germany takes, I believe, 6% p.a., I just saw on Google. Not bad, Mr. Specht, I say to that.

The tax office in Germany takes to my knowledge 12% (a whole for each month).

The tax office in D charges to my knowledge 12% (a whole for each month).

Then I'll try it too. :D

Then I'll give it a try too.

Exactly: not 12% p.a., but 1% for each started new month.