Average Monthly Balance is the measure of average monthly balance to be maintained in one's account over a certain period of time. It can also be termed as AMB or MAB. Bank use this term to show the results calculated at the end of each month. It is about closing balances of each day for the given period, usually a month. Here is the online average monthly balance calculator that lets you to find the AMB / MAB to be maintained in your account.
MAB/AMB is calculated in banks by adding all the daily closing amount balance throughout the entire month.