ORIGINAL: Okim
I`ve noticed that too. While my colonies were not taxed at all my homeworld was assigned a tax of 50%! I wonder why my people did not rebel against such tax! Turned AI off and manually adjusted taxes on all planets (so far there are less than 15 of them, so no problem with micro here). Income increased dramatically after that.
It would be nice to have a configuration possibility for this, like a slider to tell the AI how aggressively it should tax.
As it is now it keeps taxes on relatively lowly populated worlds low to encourage growth - that's not bad, and possibly much better on the long term, but if you are in financial trouble it should be possible to prioritize making some money now instead.