What documents can serve as proof of Social Security number?

The documents that can serve as proof of Social Security number are those that directly reference the Social Security number itself. The Social Security Card is the primary and most direct form of identification of one's Social Security number. In addition, W-2 Forms and SSA 1099 Forms are both official documents used by the government and employers that contain your Social Security number and are commonly required for tax purposes. Non-SSA 1099 Forms are also relevant as they report income that may be subject to taxation and include an individual's Social Security number.

In contrast, other options do not serve this purpose effectively. For example, while a driver's license or passport can serve as identity verification, they do not provide Social Security numbers. The same applies to birth certificates, tax returns, bank statements, employment letters, voter registration, utility bills, school records, library cards, and health insurance cards—they do not specifically include Social Security numbers as part of their content.