Issuing a Social Security Number (SSN)

As a rule, only persons who are not US citizens and have permission from the Department of Homeland Security to work in the US can obtain a Social Security Number. The SSN is used to send information about earnings to government agencies, to determine compliance with the criteria for receiving benefits. A Social Security number is needed to work, receive Social Security benefits, and other government services.

Non-citizens who are in the country legally can receive many benefits and services without an SSN. It is not required to obtain a driver's license, enroll in an educational institution, obtain private health insurance, apply for free school lunch programs or subsidized housing.

Some organizations use Social Security numbers to identify individuals in their records. However, in most cases it is not mandatory.

You will need it if you want to work in the United States, do business with a bank or financial institution, pay taxes or be listed as a dependent on your tax return, and for other purposes.

https://www.ssa.gov/