Using parent tag on whole gameObject

So I’ve been trying to use the hitInfo inside some OnCollisionEnter function and I want to take advantage of the tag the gameObject has:

void OnCollisionEnter (Collision hitInfo) {
		if (hitInfo.gameObject.tag == "Pad") {
			Debug.Log("Pad HIT! " +;

This won’t work! The gameObject tagged as “Pad” has lots of child objects that remain untagged. However if I try this with having the top child object tagged it works. From my understanding what is happening is that when the collision with the Pad happens Unity doesn’t see it as a collision with the whole Pad object but with one of its untagged children. Now that’s a problem because I do not want to start tagging the children I just want to have the whole parent object tagged since that’s what the rest of the environment has to interact with. How do I solve this?

EDIT: This also messes up when I try to use since it won’t recognize the gameObject. It gives me a NullReferenceException

Unity sees collisions between colliders or rigidbodies. When two colliders hit a message is sent to those specific objects. If that object or a parent of that object has a Rigidbody then physics messages are sent to those objects instead. OnCollisionEnter is one of those physics messages. hitInfo.gameObject is the game object it collided with which has the Rigidbody attached, or the collider being hit if no RigidBody is attached.

The solution is to either apply the tag to the object with the Rigidbody or put the Rigidbody (or Collider if the Rigidbody is on the other object) on the object tagged “Pad”.