Hospitals are not legally barred from seeking judgments or liens, but must first offer an aid application, help the patient complete it, and wait while it is pending. Instead, many hospitals turn to collection agencies, and sue when that fails. The unpaid bills — typically reflecting much higher rates than what insurers pay — are then treated as the equivalent of charity care.

Change is now urgent, health care experts agree, because the state pool stands to lose hundreds of millions of federal dollars in 2014, when provisions of the health care overhaul will no longer treat so-called bad debt, based on uncollected bills, as if it were charity care.

“There’s a law in place, and obviously it should be complied with,” said David Rich, an executive with the Greater New York Hospital Association, a trade group. But, he added, “hospitals are providing a lot of charity care at a loss.”

He said hospitals were improving their compliance with the law, which requires aid to patients with income up to 300 percent of the poverty line, or up to $33,000 for a single person. But, often stymied by patients who fail to complete applications for aid, he said, many hospitals have moved to simply deeming some patients eligible without an application, using what he called “a soft credit check” at registration to gauge income and assets.

Myrna Manners, a spokeswoman for NewYork-Presbyterian Hospital, said that it would be inappropriate to discuss specific cases, but that the hospital “proactively helps patients at every step” of the financial aid process. It approved 25,861 applications in 2010, the most recent annual data.