The N.C.A.A. and the richest college athletic conferences joined with plaintiffs’ lawyers on Friday to enter a $2.8 billion settlement agreement of their class-action antitrust lawsuit. The filing outlines in some detail how schools would be allowed for the first time to pay college athletes directly.

The agreement, if approved by a federal judge in California, could deliver the final hammer blow to the amateur model of college athletics, which has begun to crumble in recent years under the weight of lawsuits and legislative action.

The proposed settlement of the antitrust suit, House v. N.C.A.A., and two companion lawsuits would open the door to a new model for college athletics. As soon as a year from now, schools could begin to spend up to slightly over $20 million a year to pay athletes, a ceiling that would rise along with college athletics revenues. The arrangement would last for 10 years.

The settlement also calls for tens of thousands of football and men’s basketball players to be paid retroactively for television and marketing rights. The settlement agreement sidesteps addressing Title IX, which among other things bars colleges from treating men’s and women’s sports unequally.

The N.C.A.A. plans to use the settlement agreement as leverage with Congress to ask for a shield from further antitrust suits and from claims that athletes be considered employees.

The agreement calls for establishing an outside entity to police what are known as name, image and likeness deals for athletes. Any such agreement that is worth more than $600 would have to be reported to the athlete’s school, and a clearinghouse would be set up to help determine whether the deals have been struck at fair market value.