It is customary among banks which pay interest on demand deposits to pay interest on only what is called the cash balance of a customer's account. This can best be explained by illustration. If a customer deposits $500 of cash on June 25 and leaves it until June 30, he is entitled to five days' interest, and this is computed usually by adding five 500's, that is, $500 for each of five days, making interest on $2,500 for one day. However, if instead of cash a customer deposits checks which it requires two days to collect, he would get no interest on his deposit for the first two days on the principle that a bank cannot pay interest on money that it does not have. While it credits the depositor at once for $500 of checks received, interest does not start to accrue on the deposit until it has become a matter of available cash in the bank's possession. Assuming, then, that $500 worth of checks requiring two days to collect were deposited on June 25, the interest from June 25 to June 30 would be the equivalent of only $1,500 for one day, i. e., $500 for three days. To provide a means of withholding interest credit in such cases, the receiving teller is instructed to indicate on each deposit, by notation, the number of days a cash item must be withheld from the interest balance. Such notations are guides to the ledger clerks who place the same notations to the right of the accounts on their ledger, so that when taking off interest figures for each day the amount to be withheld from the actual balance is shown to the right of it. That makes the determination of the interest balance for each day simple. All the clerk needs to do is to deduct from the actual balance the total of the small figure notations.