I found some tax fraud error because I set the taxation of the colonies very little at the beginning of the game and then suppressed at 23:50 before each day change.
When the revenue has come you will return and the money will come, there will be no decline in population, nor will morale. As tax morale increases, you have to make several percent a day.
I looked at the two extremes, so you can switch between no tax and á la Bokros. It is important to reset to no tax at 0:00, because otherwise the residents will start to lose weight immediately. A little crappy, but the money is coming.