SPRINGFIELD — The Illinois department tasked with overseeing unemployment benefits is employing an alphabetized schedule to handle “an unprecedented volume” of claims.

Claims now must be filed online and by phone on days and at times set by the Illinois Department of Employment Security based on the first letter of the filer’s last name. Similar systems to manage “increased web traffic” and “high call volumes” were initiated in Colorado and New York as well, according to the department.

Illinoisans whose last names begin with the letters A through M may file online claims...