What is the application number used for obtaining an employer identification number?

The correct answer is the SS-4 form, which is specifically designed for entities applying for an Employer Identification Number (EIN) from the Internal Revenue Service (IRS). The EIN is crucial for businesses as it is used to identify them for tax purposes, similar to how a Social Security number identifies individuals.

When completing the SS-4 form, businesses provide essential information such as the legal structure of the business, the reason for applying, and the owner’s details, which the IRS reviews to issue the EIN.

The other forms listed serve different purposes: IRS-99 is not an actual form for EIN application; the W-2 is a form used to report wages paid to employees and the taxes withheld, and Form 941 is a quarterly payroll tax return used by employers to report income taxes, Social Security tax, and Medicare tax withheld from employee wages. Each of these forms plays an important role in payroll processing and tax reporting but is unrelated to the application for obtaining an EIN.