Why I first ask ITIN applicants reason for applying:
One cannot arbitrarily apply for an ITIN and I work with clients to identify facts that clearly place them into one of the finite IRS reasons accepts for applications.
A few examples where ineligibility isn't intuitive are (per IRS ITIN dept):
IRS assigns ITINs for federal tax purposes only; therefore, the individual is not eligible for an ITIN if the sole purpose for requesting a number is to provide to a state for sales tax registration purposes. This does not constitute a federal tax purpose.
Form W-7 should not be submitted if the individual does not have to file a federal tax return (1040 series) or have an IRS reporting or federal withholding requirement. [I understood this IRS comment as said in the context of where a filing exception did NOT apply.]
ITINs are not issued to facilitate the establishment of a financial account, as this does not constitute a federal tax purpose.
There are many nuances to the process (such as when an envelop, marked with applicant's name, received in mail by applicant must be included) and each application's form completion and attached documentation differs from the next - with such variance based upon reason applied for
For some client situations I recommend insted applying for a tax ID (TIN) other/different than an ITIN