American homeowners could see a significant drop in the cost of selling their homes after a real estate trade group agreed to a landmark deal that will eliminate a bedrock of the industry, the standard 6 percent sales commission.

The National Association of Realtors, a powerful organization that has set the guidelines for home sales for decades, has agreed to settle a series of lawsuits by paying $418 million in damages and by eliminating its rules on commissions. Legal counsel for N.A.R. approved the agreement early Friday morning, and The New York Times obtained a copy of the signed document.