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...