New York's charity care system, partly financed by an 8.95 percent surcharge on hospital bills, is one of the most complicated in the nation, but many states have wrestled with aggressive debt collection by hospitals in recent years. Like New York, several passed laws curbing hospitals' pursuit of unpaid bills, including Illinois, California and Minnesota. But a new study of New York hospitals' practices and state records finds that most medical centers are violating the rules without consequences, even as the state government ignores glaring problems in the hospitals' own reports.