The State Insurance Department has levied its biggest fine ever – more than $100,000 – against an HMO based in Chesterfield. Insurance Director Scott Lakin says Mercy Health Plan violated the state’s prompt pay law by failing to acknowledge receipt of about 20 percent of the claims filed with it. The law requires HMOs to acknowledge claims within ten days. Lakin says Mercy has paid its fine promptly, without objection. He adds several more companies are being examined.