Most likely it's due to reconciling items just like on a bank statement reconciliation. There are sales that happened on the last day or two of the month that won't show up until the following month. There could be a couple of explanations for this such as, 1) did bank cutoff date not extend to the actual last day of the month. Some banks will cutoff a statement on the 29th because it's the last business day of the month. 2) Were the sales receipts deposited in a timely fashion [before the bank closed for the day for example]. Try to reconcile the two amounts and see if this doesn't get you where you want to go.
