A Bank reconciliation is a process that explains the difference between the bank balance shown in an organization’s bank statement, as supplied by the bank, and the corresponding amount shown in the organization’s own accounting records at a particular point in time.
Such differences may occur, for example, because a cheque or a list of cheques issued by the organization has not been presented to the bank, a banking transaction, such as a credit received, or a charge made by the bank, has not yet been recorded in the organization’s books, or either the bank or the organisation itself has made an error.
It may be easy to reconcile the difference by looking at very recent transactions in either the bank statement or the organisation’s own accounting records (cash book) and seeing if some combination of them tallies with the difference to be explained. Otherwise it may be necessary to go through and match every single transaction in both sets of records since the last reconciliation, and see what transactions remain unmatched. The necessary adjustments should then be made in the cash book, or any timing differences recorded to assist with future reconciliations [source wikipedia]