Game concept
Taxpayer
The game also links it as Taxpayers.
From the game's encyclopedia
Taxpayers are Clan Vassals that have been assigned to a Tax Jurisdiction, and will contribute monthly Tax Income and Levies as long as a Tax Collector is appointed.
The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.
Taxpayer is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Taxpayers are Clan Vassals that have been assigned to a Tax Jurisdiction, and will contribute monthly Tax Income and Levies as long as a Tax Collector is appointed." It is part of Tax Jurisdiction. It covers Untaxed Vassals. The game also links it as Taxpayers. Patch 1.20.1.2, from game/common/game_concepts/03_fp3_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/03_fp3_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.