Why do you want an ITIN?
The IRS assigns an Individual Tax Identification Number (ITIN) so that non-Americans can file US income tax returns. An ITIN is useful for other reasons. For example, when paying real estate taxes, you may be asked for your ITIN. However, before you can get an ITIN, you need to show the IRS a federal tax reason.
If you are applying for a US residency permit (Green Card), the IRS will not issue you an ITIN until you receive your Green Card. This is because the IRS requires a specific tax reason in order to assign an ITIN, and obtaining a residency permit or green card falls into the category of immigration-related reasons.
Many people request an ITIN because they need the number to open an account in the US or online, for example, to get a US Bank Account. You can get an ITIN to open a bank account, but you might not be able to get the personalized letter from the bank that the IRS requires. We have more information about the required documents here.
The IRS will reject an ITIN application unless you show a federal tax reason. If you are not filing a US income tax return, your reason needs to fit into one of what the IRS calls "Exceptions", which relate to US income or withholding tax.
IRS-Approved Reasons