How can I update the registrant / owner details of a .IE domain name?

For any registrant changes with a .ie we would need a signed fax on the organisation’s letterhead outlining the update
For example, if XYZ Ltd had registered back in 2002 when Mr John Doe was their IT person Mr Doe might be listed as the Admin contact (admin-c) on the domain name.
Time moves on and Mr Doe has left the company (or maybe he’s been promoted ..) so Ms Jones is now in charge.
The domain is still registered to XYZ Ltd, but you need to get the domain contact updated. A signed fax on the company’s headed paper explaining the update should suffice.