Final answer:
Form number A. W-7 is used by individuals who are not eligible for a social security number to request an Individual Taxpayer Identification Number (ITIN) for federal tax reporting purposes.
Step-by-step explanation:
Aliens who are not eligible for a social security number and must file a tax or information return would request an Individual Taxpayer Identification Number (ITIN) using form number A. W-7. The ITIN is used for federal tax reporting purposes, allowing individuals who are not eligible for a social security number, such as non-residents or resident aliens, to comply with U.S. tax laws. It plays a vital role in ensuring that everyone, regardless of citizenship status, pays the taxes they are legally obligated to pay.