More than 90,000 Long Island families could face a $250 surcharge on federal flood insurance policies if they overlook paperwork to prove the coverage is for their primary residence, Sen. Charles Schumer warned Monday.

The Federal Emergency Management Agency began assessing the charge last month to homeowners who failed to return "proof of residency" forms within 30 days. Schumer (D-N.Y.) said policyholders need more notice.

"I'm not sure where FEMA is coming from on this, but they are making it extremely difficult for people," Schumer said.

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The annual surcharges were ordered last year by Congress to shore up the finances of the National Flood Insurance Program, which is $23 billion in debt. The law calls for homeowners to pay surcharges of $25 on policies covering their primary residences and $250 on those covering vacation homes or rental properties.

FEMA, which oversees the flood insurance program, sent homeowners questionnaires to determine which surcharge applied to their policy. If they don't fill them out, they are automatically charged $250.

A spokeswoman for the agency said the companies that administer the polices have not reported widespread billing errors as a result of homeowners' overlooking "proof of residency" forms.

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Schumer, however, said less than 4 percent of the 140,000 flood insurance policies on Long Island and in New York City cover second homes. The onus to determine those, he said, should fall on FEMA.

The senator is asking the agency to stop defaulting to the $250 surcharge and devise a system that is "far less onerous."