How Does the Final Settlement Mechanism Enforce Convergence for Cash-Settled Futures?

The final settlement mechanism enforces convergence by defining the final settlement price as the underlying spot price (or a highly correlated index) at expiration. Since the contract is settled against this spot-based price, the futures contract's price must converge to it by the expiration date.

If it did not, an immediate, risk-free profit could be made by trading the final moments of the futures contract against the underlying index.