Net interest margin is the percentage return on assets a company earned once borrowing expenses (IE, interest paid to depositors such as individuals with saving accounts or to financial lenders) are taken into account.
Net interest margin is similar to Net Interest rate spread in that both refer to the percent a company earns on assets once the cost of borrowing those assets is taken into account, but Net Interest Rate Spread is a hypothetical number that a company could earn if all assets were borrowed and invested at the going rates. In reality, some assets are, for example, kept in non-interest bearing accounts and therefore may incurr borrowing costs without earning any interest. Net Interest Margin takes this into account and is the percentage return the company actually achieved in the real world.
