US citizens and noncitizen nationals generally don't need reverification. For other employees, you need to re-verify their documents if they expire.
According to the United States Citizenship and Immigration Services (USCIS), you don't need to reverify
List B includes driver's license, state ID cards, voter's registration card, Native American tribal document, and other documents.
However, if an employee presented a foreign passport that contains a temporary I-551 stamp, you'll need to re-verify the authorization just prior to the stamp's expiration date in order to remain in compliance.
If an employee is a minor (under the age of 18), they are subject to the same re-verification rules as other employees. Minors can present any of the standard List B documents, or:
Immigrations and Customs Enforcement (ICE) may conduct an audit to ensure your company's compliance. ICE may request that you produce the following documents:
If you knowingly employ ineligible workers, or fail to produce current and accurate documents, ICE may deem that you had knowledge that the worker wasn't eligible to work in this country, and assess a fine or pursue legal action.
As with any other office protocol, consistency is key. Internal procedures should include:
Inoculating Your Business Against an Outbreak: I-9 Compliance - How to avoid I-9 compliance issues.