I-9 forms verify:

The I-9 form is a critical document used in the United States to verify an individual's eligibility to work. This form requires employees to provide specific documents that establish both their identity and their authorization to work in the U.S. By completing the I-9 form, employers ensure that they are not hiring individuals who are not legally permitted to work in the country, making it a vital component of employment verification processes.

On the other hand, the other choices do not pertain to the purpose of the I-9 form. Criminal records, for instance, are not part of the I-9 verification process, nor does the form address payment of income taxes or age eligibility, which are covered by other regulations and forms in the employment landscape. Therefore, the focus of the I-9 form is solely on confirming a person's eligibility to work in the United States.