The information at the link below was quite helpful to me and includes a link to the IRS’ W7 form.
An Individual Taxpayer Identification Number (ITIN) is assigned by the Internal Revenue Service to individuals involved in a transaction which may be a
au.usembassy.gov
From re-reading the web page appears that the ITIN needs to be renewed every three years if not used to lodge a US tax return.
I Read somewhere it can take up to 7 weeks to get it back. I applied the last week of November. Might take longer because of the holidays. I’ve had a look on the form again doesn’t seem to ask for any reason. Mine if asked would be I intend to make investments in the US. Will post when I hear back. I notice (but haven’t used) there is a site EIN where it can be done electronically for a similar cost. I haven’t used that site so can’t give any feedback.
Keen to hear of others’ experiences in getting an ITIN if it took 7 weeks or longer and how well it’s worked.