Visa question of the month - visa expires during stay in USA

No. Your employee may legally reside in the United States of America for the period of time and purpose granted to him/her upon entry by U.S. Customs and Border Protection officers of the U.S. Department of Homeland Security (DHS) (= approved residency status).

Visa holders receive an entry stamp in their passport, which indicates the date of entry, the visa category and the date on which he or she must leave the U.S. at the latest. The information on the residence status is available in the I-94 entry form.

Thus, it may well be that your employee's US visa is expiring or has expired, but he or she still has legal residency status.
It is best for the employee to double check their passport or I-94 to see exactly how long they are allowed to stay in the US.

Please note: If the employee leaves the US on time, he or she requires a new US visa for re-entry, provided it is for the same purpose of stay. A personal interview at the US consulate in the home country would again be mandatory for the visa to be issued. For visa renewals, a postal submission process may also be used under certain circumstances. Allow sufficient time for this.

Check here your current I-94 Status including the exact date of departure.:https://i94.cbp.dhs.gov/I94/#/home#section