Japan is one of the countries that listed on the treaty with us taxes. So For especially Japanese How they can get the Id tax number?
Your government issues your tax id number. You need to get it from your government. I’m sure you can find instructions online specific to your country.
Then what if I use my friend tax id number in Envato market to avoid the Royalty tax is it eligible or not?
Is your friend okay with paying taxes for you?
I’m not 100% sure but I don’t think it would be allowed; the identity you submit on the tax form, as far as I know, must represent the owner of the Envato account. By doing that you’re giving your friend ownership over all of your sales, earnings, etc.
You can send questions to firstname.lastname@example.org to get reliable answers to questions like this.