Where are IAG shares registered?

Excuse me, I'm curious about the registration of IAG shares. Could you please elaborate on where exactly these shares are registered? Is there a specific financial institution or regulatory body that oversees this process? Additionally, is there a specific process that shareholders need to follow in order to ensure their shares are properly registered and accounted for? I'm looking to gain a better understanding of the mechanics behind share registration and how it applies to IAG specifically. Thank you in advance for your insights.