It would appear the process has changed since I did it. If you live in a country with a national tax id number, you can now use that. However, you can also elect to use an ITIN or EIN even though no US tax return is required.
“ If you are a non-U.S. publisher interested in claiming tax treaty benefits to reduce your withholding, you will have to provide a tax identification number (TIN). If you have a U.S. TIN (ITIN for individuals, EIN for non-individuals), you must provide it. If you do not have a U.S. TIN and the tax authority in your country of residence issues an income tax identification number, you may enter it to claim treaty benefits.”
“ If you are a non-U.S. publisher interested in claiming tax treaty benefits to reduce your withholding, you will have to provide a tax identification number (TIN). If you have a U.S. TIN (ITIN for individuals, EIN for non-individuals), you must provide it. If you do not have a U.S. TIN and the tax authority in your country of residence issues an income tax identification number, you may enter it to claim treaty benefits.”
https://www.savvynewcanadians.com/amazon-kindle-self-publish...