Not required but recommended. This is from the attorney.
When an employee has an I-140 approved and an AOS pending for at least 6
months, he/she has the option to change employers and “port” the
application to the new employer under AC21 rules. However USCIS would like
the employee and employer to notify USCIS of the change. This is not a law
…it is a USCIS policy. It is not required but it is highly recommended by
the District Director.
