When you get foreign payments > 12.5k in a month, you need to report them to the Bundesbank. You can do that online. But only on weekdays and from 9am to 4pm on Saturday, because ... I suspect it's labor laws and to be safe they assume servers have to be treated as employees.

I'm not joking: https://www.bundesbank.de/de/service/extranet/-/zugangszeite...

And they enforce it, too. Logging in on a Sunday will only get you an error message.