Initial taxes
 

Maybe this is common knowledge, but it turns out that when you conquer a province initially it's taxed at 100%, but (I think) the unrest from whatever taxation rate was set before still takes effect. I mention this because I was considering setting taxes to 0% just before an enemy takes a province, but it won't work. On the other hand that means there's no downside to setting taxes to 200% before losing a province--it generates unrest for him, and if you guessed wrong about his intentions you get an extra turn of high income.

-Max

Re: Initial taxes
 

newly conquered provinces are taxed according to their unrest, when you select it you will find the "auto-tax" box always checked... so taxes are at most 100%, when unrest is 0.