New York made away with $320 million from the federal government by over-billing Medicaid, according to a new watchdog report.

According to the inspector general for the Health and Human Services Department, state-operated residences billed the federal government at twice the rate charged by privately operated residences offering the same "habilitation services" in 2010.

"Habilitation services" offered by the state's Office for People with Developmental Disabilities help individuals with developmental disabilities "acquire and retain skills related to living in the community," according to the IG report.

By double-billing the government, Medicaid paid New York $320 million — or 57 percent — more than actual costs.

The average Medicaid payment was $18,759, while the average at the privately operated residences was $8,302.

Had the Centers for Medicare and Medicaid Services made sure New York was making efficient payments based on actual costs, the government would have saved $346 million in 2011.