I'm opening a UG as I'm getting more interest in my SaaS (yay!). However, I'm going the bootstrapped way, and it really hurts having to pay a tax advisor 100+ euro/month, mostly just to upload some data to the Finanzamt. I will just make a couple of customer invoices per month, plus I pay for those 2-3 software tools - nothing crazy.

Is having a tax advisor really the only way? I've seen some tools to keep track of invoices etc, but most seem to still need a tax advisor for the last step. Is there any way to learn about this myself? Any tip is appreciated.