Definition of 'Excess Reserves'
Capital reserves held by a bank or financial institution in excess of what is required by regulators, creditors or internal controls. For commercial banks, excess reserves are measured against standard reserve requirement amounts set by central banking authorities. These required reserve ratios set the minimum liquid deposits (such as cash) that must be in reserve at a bank; more is considered excess.
Investopedia explains 'Excess Reserves'
Financial firms that carry excess reserves have an extra measure of safety in the event of sudden loan losses or cash withdrawals by customers. This may increase the attractiveness of the company that holds excess reserves to investors, especially in times of economic uncertainty. Boosting the level of excess reserves can also improve an entity's credit rating, as measured by ratings agencies like Standard & Poor's.
Reserves need to be in liquid forms of capital such as cash in a vault, which does not create income. Banks will therefore try to minimize their excess reserves by lending the maximun allowable amount to borrowers.