Taxation

Taxation is how Houses raise income. The Head of a House has the authority to raise and lower taxes on their subjects.

Codex
"Tax is the primary source of income for ruling, leading, and great houses. Each direct vassal of a house pays tribute to their master house.

How much of a vassal's surplus is a fair tribute is a source of never-ending conflict between master and vassal. At least within a colony, the portion that is fair is a matter of long-standing custom, and disputes are restricted to arguments on the productivity of a house. Vassals naturally hide the true scope of their income, and a large part of what your Administrators will do is try to ferret that out.

You can set the portion of their surplus that rulers in your faction, or leaders in your league, must pay. Note that colonies whose ruler is your direct vassal will provide more revenue than colonies that are the direct vassal of one of your vassal leaders, since those leaders keep a portion of the tax revenue raised."