Score decreases on collision

Unity Engine
1 
#pragma strict

var score : int = 0;
function Start () {


}

function Update() {
score++;
guiText.text = "Score = 0:" +score;
}

function  OnControllerColliderHit(col:Collision){
if(col.gameObject.tag == "GUI"){ 
    score -=300; 
Destroy(col.gameObject);
Debug.Log("stain");
}
}

function OnControllerColliderHit is not being called somehow
how do i make the score decrease by 300 everytime the player collides with something?

2

Does that game object have a collider on it, both of them? Does the object you are colliding with have a tag of GUI?