When a customer at the bank gets a hold of a statement in through the mail, the statement lists out all the transactions happened during previous month. The transactions include both incoming and outgoing, tallying up to a final sum which is indicated as the up-to-date account balance for the benefit of the customer. Without the benefit of the statement, the customer would be much more in the dark more with respect to the contents of the account. With the statement in hand the customer knows details such as the dollar value spent, the size of the income, and the present state of the account.
The fact of the matter is that this information becomes outdated almost immediately as the customer starts to use money. A simple ATM withdrawal means the account balance is not reflected in the monthly statement. The way to make sure one knows the state of finances even between statements is known as "bank reconciliation". The device to help one do so is the checkbook register - which is simply a little sheet of paper that is used for recording transactions.
What is the importance keeping track of this money? The larger fraction of bank customers have come up against deep reasons to do so. Indeed, whenever a check is issued with a value higher than the level of money in the account, two things happen. The check may not go through incurring a bounced check fee, or the check goes through because the bank covers it temporarily triggering an overdraft fee. In both cases there is a serious negative consequence.
The types of transactions are many. Monthly car payments by way of check can result in a penalty if there are not enough funds on the day the payment is being cashed.
Personal checkbook registers impedes the rotten luck of such errors occuring. For people who have trouble managing their finances but also find maintaining a checkbook register too burdensome, there are electronic alternatives which are faster and easier to use. These are merely calculator-like devices that can easily be carried around. They have special entry keys for the different kinds of transactions one might encounter related to the checking account.
Very recently the U.S. Senate implemented a series of consumer-friendly finance rules relating to how banks charge overdraft fees (this fee is incurred whenever a bank steps in and pads a customer's account whether or not the customer wants it). Basically a bank must ask a customer to opt-in to their overdraft fee program. However, the flip side is that without the overdraft fee, checks will bounce and cause other kinds of trouble. Therefore, it is still best to keep finances in check with devices like the checkbook register.