BOSTON—Massachusetts regulators have slightly reduced the surcharge on services received at hospitals and ambulatory surgical centers in the state.

The surcharge, which applies to bills paid on or after Oct. 1, will be 1.55%, down from 1.9% in fiscal 2010, which ends Sept. 30.

The new surcharge assessment, announced Monday by the Massachusetts Division of Health Care Finance & Policy, is imposed on third-party claims administrators, health maintenance organizations, preferred provider organizations and employers that administer their own health care plans.

Massachusetts uses the surcharge revenue to reimburse hospitals for care provided to the uninsured. However, under the state's 2006 health care reform law, a greater portion of the revenue has been shifted to subsidizing health insurance premiums of lower-income, uninsured state residents.