Do I need a local tax ID number to register .CL domains?

No. Beginning in December 2013, NIC CL is no longer requiring that domains be registered under a local tax ID number (RUT). However, if you do possess a valid RUT, we reccomend that you input this value when registering domains. This could serve to demonstrate a real connection to a local entity in the event that you ever needed to defend your interest in the domain, or if the NIC altered its policies in a way that led to increased relevance of the RUT.