A former employee has filed a lawsuit against the nation’s largest pool and spa retailer, citing an often misunderstood law involving overtime pay.

Keith Cunningham worked for Phoenix-based Leslie’s Poolmart Inc. from September 2011 to September 2012. He filed the suit in California Superior Court in Los Angeles against his former employer, claiming he had not been paid overtime wages due him. Cunningham has requested that the case be made a class action, stating that many others have been affected.

Collective suits alleging wage and hour violations have spiked dramatically in recent years, increasing nearly 400 percent since 2001, records show. Many of the cases in the past decade revolve around bonuses.

Legally, a nonexempt employee’s pay rate is calculated using an hourly wage along with any “nondiscretionary” bonuses, including incentives and commissions. Thus, if a staff member is paid a bonus of that kind within the same pay period that overtime is worked, the bonus must be included as part of the base wage when calculating the time-and-a-half overtime rate.

The complaint against Leslie’s charges that even though a nondiscretionary bonus was part of Cunningham’s pay structure, his overtime wages were based only on his hourly rate of $12, and didn’t include the bonus. He claims the company made the same mistake with enough employees to constitute a class.

“This uniform policy and practice of [Leslie’s] is intended to purposefully avoid the payment of the correct overtime compensation as required by California law, which allows [Leslie’s] to illegally profit and gain an unfair advantage over competitors who complied with the law,” the complaint further alleges.

Additionally, the suit charges that Leslie’s failed to have a policy of providing mandated meal and rest breaks to Cunningham and other members of the class.

The complaint did not detail how much money Cunningham believes he is owed.

As far as bonuses, the code is an easy one to overlook and can seem counterintuitive, explained Dana Kravetz, chairman of the labor and employment department at the Los Angeles office of Michelman & Robinson. (Kravetz and his firm are not involved with the case.)

“The rub, I suppose, is this: You’re already giving a bonus and now you’re paying overtime on [it],” Kravetz observed. “It’s an expense to the employer that they weren’t necessarily aware of.”

In filing the case as a class action, Cunningham seeks to add any Leslie’s employee in California who worked under a similar pay plan for the four years preceding the suit’s filing date of Feb. 13.

Leslie’s officials would not comment for this story, citing ongoing litigation.

Founded in 1963 as a one-man pool-supply operation in a Los Angeles suburb, Leslie’s now operates more than 770 retail and commercial service stores in 35 states.