What is my TAX ID

Your tax ID is either your SS# or your ITIN.

Your tax ID is your own Social Security number--or if you do not have a Social Security number it could be your ITIN.  There are some people who get a Tax Identification number to use instead of having to give out a Social Security number when they are going to get a 1099Misc for work as an independent contractor.  Did you get a Tax ID from the IRS for a purpose such as that?

https://www.irs.gov/individuals/international-taxpayers/taxpayer-identification-numbers-tin