What does the Independence casus belli cost?

prestige; the amount depends on the titles, claims and distance, worked out when you declare.

Casus belli · Independence

Independence

The war is called “Independence War”

Independence is a casus belli in Crusader Kings III (independence). If the attacker wins: The attacker is released from their Tributary obligations to the defender. If the defender wins: The attacker remains a Tributary of the defender. Declaring it costs prestige. The war goal is worth 80% war score. Patch 1.20.0.3, from game/common/casus_belli_types/00_tributarize.txt.

Quick answers (3)

What do you get for winning a Independence war in CK3?: The attacker is released from their Tributary obligations to the defender (patch 1.20.0.3).
What happens on a white peace?: The attacker remains a Tributary of the defender.
What does the Independence casus belli cost?: prestige; the amount depends on the titles, claims and distance, worked out when you declare.

How the war ends

Attacker wins

The attacker is released from their Tributary obligations to the defender.

White peace

The attacker remains a Tributary of the defender.

Defender wins

The attacker remains a Tributary of the defender.

If the war becomes invalid

The … has ended: it was no longer valid to continue.

Who can declare it

The game shows no text of its own for these conditions; the script is below.

Every independence war (the group's allowed_for_character) (1 line of game script)

pam_personal_pacifism_offensive_war_ban_trigger = yes

As written in game/common/casus_belli_groups/00_casus_belli_groups.txt.

Attacker (allowed_for_character) (6 lines of game script)

scope:attacker = {
	this != suzerain
	NOT = {
		obedience_target ?= suzerain
	}
}

As written in game/common/casus_belli_types/00_tributarize.txt.

Defender (allowed_against_character) (3 lines of game script)

scope:attacker = {
	suzerain = scope:defender
}

As written in game/common/casus_belli_types/00_tributarize.txt.

Cost to declare

Costs prestige. The amount is worked out when you declare (by the titles targeted, claims, distance and more), so the script is shown as written:

Cost (8 lines of game script)

prestige = {
	value = 0
	add = {
		value = 100
		desc = CB_BASE_COST
	}
	multiply = common_cb_prestige_cost_multiplier
}

As written in game/common/casus_belli_types/00_tributarize.txt.

Source: game/common/casus_belli_types/00_tributarize.txt and the English localisation, Crusader Kings III 1.20.0.3. “The attacker”, “the defender” stand where the game names the character; “…” marks other words it fills in during play.