PlayInfoBox

Home /Education /Form I-9 Basics: How US Employment Eligibility Verification Works

Form I-9 Basics: How US Employment Eligibility Verification Works

Nearly every new US employee fills one of these out in their first days on a job, yet many people never fully understand what it actually verifies.

It verifies identity and authorization to work, not tax status

Form I-9 exists to confirm both who a new employee is and that they are legally authorized to work in the United States. It is a distinct requirement from tax forms like the W-4, which instead determine how much income tax is withheld from pay.

Section 1 must be completed by the employee's first day of work

The employee fills out Section 1 with their own identifying information and attests to their work authorization status no later than their first day of actual employment, though it can be completed earlier once a job offer is accepted.

Section 2 must be completed within three business days of starting

The employer, or the employer's authorized representative, must physically examine the employee's original identity and work-authorization documents and complete Section 2 within three business days of the employee's first day of work for pay.

Employees choose from List A, or List B plus List C

A List A document (like an unexpired US passport) establishes both identity and work authorization on its own. Alternatively, an employee can present one document from List B (establishing identity, like a driver's license) together with one from List C (establishing work authorization, like a Social Security card).

The employee chooses which acceptable documents to present

Employers are not allowed to demand a specific document or combination of documents from an employee, or refuse otherwise-acceptable documents that reasonably appear genuine, as long as the employee presents a valid combination from the official lists.

Employers must retain I-9s for a set period, even after termination

Completed I-9 forms generally must be retained for three years after the date of hire, or one year after employment ends, whichever date is later β€” meaning the form often has to be kept well beyond the employee's last day.

E-Verify is a related but separate, additional system

E-Verify is an online system that electronically cross-checks I-9 information against government records; it is not required for every US employer, though federal contractors and, in some states, most or all employers are required to use it β€” requirements vary by state and can change.

Some employees need reverification later

If an employee's original work authorization document had an expiration date, the employer is generally required to reverify that authorization before it expires, using the dedicated reverification section of the current form rather than starting an entirely new I-9.

Why this form exists separately from tax paperwork

Form I-9 and tax forms like the W-4 serve entirely different government purposes β€” one confirms legal eligibility to work at all, administered under immigration-related employment law, while the other determines payroll tax withholding. New employees often fill both out in the same onboarding packet, which is a common source of confusion about what each one actually does.

The document lists exist to standardize a subjective process

Because acceptable identification varies so much by state and by individual circumstance, the official List A, B, and C system gives employers a defined, limited menu of documents to check rather than leaving acceptability up to case-by-case judgment, which also protects employees from being asked for documents beyond what the law actually requires.

Frequently Asked Questions

Is Form I-9 the same as a tax form?

No. Form I-9 verifies identity and work authorization; it is unrelated to tax withholding, which is instead handled by separate forms like the W-4 for federal income tax purposes.

Can an employer ask for a specific document, like only a passport?

No. As long as an employee presents a valid, acceptable combination of documents from the official lists, the employer cannot require a specific document or reject genuine-looking, acceptable documents in favor of a preferred one.

How long does an employer have to keep completed I-9 forms?

Generally three years after the date of hire, or one year after the employment relationship ends, whichever of those two dates comes later.

Is every employer required to use E-Verify?

No, not universally β€” E-Verify is mandatory for many federal contractors and, in some states, for most or all employers, but requirements vary by state and have changed over time, so it is worth checking current state-specific rules.