A check book unit has a card reader and a PDA-type system. Check transactions are recorded in the unit using the PDA-type unit and a computer keeps track of the balance and other data associated with the check transaction. A card reader is also included and uses one of the magnetic stripes on a debit card. After a debit card is used, the details of the transaction are recorded onto the magnetic stripe. When the debit card is swiped through the card reader on the unit, the details of the transaction are transferred into the computer memory associated with the unit. The computer then records the details of the transaction from the data entered on the debit card and performs the arithmetic required to balance the user's check book balance.