As mandated by the Internal Revenue Service, every individual who is authorized to work in the U.S. must have a Social Security number, and must file Form SS-5 after a name change.
As mandated by the Internal Revenue Service, every individual who is required for U.S. tax purposes to have a U.S. Taxpayer Identification Number, but who is ineligible for a Social Security number, must attach Form W-7, Application for IRS Individual Taxpayer Identification Number, to the income tax return for which the Individual Taxpayer Identification Number is needed.