Taxation is managed via the finance panel. Its taxes tab shows a summary of your projected income, maps the effect that the current tax rate is having on public order and wealth, and allows the adjustment of tax levels globally for every province under your control. AI management of taxation (auto-management) can be specified here. Click on the button at the bottom of the panel to go straight to the province details panel of the province with the lowest public order. In most cases, adjusting tax levels should fix the problem, although it is also possible to exempt a province from taxation there.
Managing Your Finances
A financial summary is issued each turn. It can be accessed via the summary tab on the finance panel.