Can I apply for an ITIN if I already have a Social Security Number?
No, you cannot apply for an Individual Taxpayer Identification Number (ITIN) if you already have a Social Security Number (SSN). The Internal Revenue Service (IRS) explicitly states that ITINs are only issued to individuals who are not eligible to obtain an SSN.
If you already have an SSN, you are expected to use it for all tax-related purposes. Applying for or using an ITIN when you have an SSN is not permitted.