"Unpaid overtime" refers to the extra hours someone works beyond their regular work schedule without receiving additional pay for that extra time. Full definition
Forty - eight per cent are regularly working more than one extra hour a day and one in 10 admitted to working three of more hours of unpaid overtime every day. (educationbusinessuk.net)
And it's not just claims for unpaid overtime that shouldn't necessarily be brought as class actions. (toronto-employmentlawyer.com)