> Estimate your revenue at 0€ for now unless you have real reason to believe otherwise (do you have paying customers lined up already? probably not). That way, you only have to pay corporate tax at the end of the year based on your actual profit (vs. having to prepay tax every quarter).
This is funny. I tried to set my revenue to 0 in the beginning and the tax authority simply set it to 60k (they couldn't even tell me where this number came from). After a couple of harsh phone calls (from their end, they were yelling) they simply kept it and told me I could file a "Verwaltungsklage". Of course, they (and IHK) derive the quarterly pre-taxes from that and didn't give a rats ass if I actually made any revenue. I got my money back a year later (which got worse and worse over time). Simply kills you, If you have to pay the bills and try to route your little boat through the stormy seas. Several times I spontaneously had to credit 2-3k EUR to get my customers to shorten the term of payment.
> IHK: Domains are not allowed.
This is funny as well because my company name was a domain name. IHK noticed that and I told them (on phone w/o any proof) that it's mine and they were okay.
The rest, I'd say is batshit crazy bureaucratic but somehow manageable. Germany is just not a good spot for "some SaaS idea" or maybe not even for bigger ideas as well anymore. At least not until they radically streamline their bureaucracy (which depends on radically professionalized politics which is not realistic at this time).
PS: Founding a company made me stop believing in "Social Market Economy" (German self-label) since the taxation system and social systems allow for amazing things once you're out of the employee system.
Edit: Typos and grammatical mistakes.