Simply put, if a PERM form requires employment experience, then the I-140 petition should provide an employment verification letter as contemplated in the regulations.

An employee verification letter serves two purposes. One, it shows that the employee has a job. It can also help determine if the employee is a temporary employee or a full-time, permanent member.

DHS Designates E-VERIFY Employment Eligibility Verification System for Federal Contractors ... as the electronic employment eligibility verification system that all federal contractors must use ...