Worker demands back overtime? Investigate and, if warranted, pay up.

If an employer pays overtime incorrectly, it may be liable for up to two years of unpaid overtime, doubled as a penalty. But if an employer's overtime mistake is "willful," that liability reaches back another year, adding to the cost.

Judges typically find a willful violation if an employee asked about overtime pay discrepancies and the employer didn't bother to investigate the matter.

Recent case: Susan worked for 14 years as a scheduler at the Maternal Child Consortium. She regularly worked 41.5 hours per week at the worksite. She also put in additional "on call" hours when she had to carry a company cell phone and the schedule, answering three or four calls per on-call period. She never received overtime pay.

After the employer fired Susan following an illness, she sued, claiming she should have been paid overtime...