tribute_mission_invalidation_effect

tribute_mission_invalidation_effect = {
	if = {
		limit = { has_variable = tribute_mission_type }
		if = {
			limit = { # sanity check to ensure we're still a valid tribute provider
				OR = {
					is_independent_ruler = no # if we have a liege we cannot also pay tribute to someone else
					AND = { # if we're not a tributary we are only valid if we're paying tribute to a hegemony
						is_tributary = no
						OR = { 
							NOT = { exists = var:tribute_mission_target_scope }
							var:tribute_mission_target_scope = { NOT = { highest_held_title_tier = tier_hegemony } }
						}
					}
				}
			}
			#Return home and refund
			trigger_event = tribute_mission.9800
		}
		else_if = { #If our offerings have perished or been imprisoned along the way, maybe swap to gold
			limit = {
				has_variable = tribute_mission_type
				OR = {
					AND = {
						has_variable = offered_concubine
						OR = {
							var:offered_concubine = { is_alive = no }
							var:offered_concubine = { is_imprisoned = yes }
						}
					}
					AND = {
						has_variable = offered_eunuch
						OR = {
							var:offered_eunuch = { is_alive = no }
							var:offered_eunuch = { is_imprisoned = yes }
						}
					}
				}
			}
			trigger_event = tribute_mission.9750
		}
		else_if = {
			#We're still a tributary on our way to pay tribute, but our suzerain is not the person we were going to pay tribute to
			limit = {
				has_variable = tribute_mission_target_scope
				OR = {
					AND = {
						is_tributary = yes
						var:tribute_mission_target_scope != suzerain
					}
					AND = {
						is_tributary = no
						OR = { 
							NOT = { exists = var:tribute_mission_target_scope }
							var:tribute_mission_target_scope = { NOT = { highest_held_title_tier = tier_hegemony } }
						}
					}	
				}
			}
			var:tribute_mission_target_scope = { save_scope_as = old_overlord }
			suzerain = { save_scope_as = new_overlord }
			#Clean up Requested Tribute Mission variables
			requested_tribute_mission_clean_up_variables_effect = yes
			#The new Overlord is in the same place and can accept the tribute
			if = {
				limit = { 
					#Make sure they can still accept our offerings; if so, just set the new target
					current_travel_plan.next_destination_province = scope:new_overlord.capital_province
					has_variable = tribute_mission_type
					trigger_if = {
						limit = {
							has_variable = {
								name = offered_concubine
								name = offered_eunuch
							}
						}
						OR = {
							AND = {
								has_variable = offered_concubine
								var:offered_concubine = {
									can_become_concubine_of_character_valid_trigger = { CHARACTER = scope:new_overlord }
								}
							}
							AND = {
								has_variable = offered_eunuch
								scope:new_overlord = { 
									culture = { has_cultural_parameter = can_appoint_chief_eunuch } 
								}
							}
						}
					}	
				}
				send_interface_message = {
					type = msg_mandala_neutral_text
					title = tribute_mission_notification.new_overlord.title
					left_icon = scope:new_overlord
					desc = tribute_mission_notification.new_overlord.desc		
				}
				set_variable = {
					name = tribute_mission_target_scope
					value = scope:new_overlord
				}		
			}
			#The Overlord is somewhere else; please try again
			else_if = {
				limit = {
					current_travel_plan.next_destination_province != scope:new_overlord.capital_province
				}
				set_variable = new_overlord_somewhere_else
				#Return home and refund
				trigger_event = tribute_mission.9800
			}
			else = {
				set_variable = new_overlord_unable_to_accept_tribute
				#Return home and refund
				trigger_event = tribute_mission.9800
			}
		}
	}	
}

As written in game/common/scripted_effects/tgp_tribute_mission_scripted_effects.txt.