There are two types of debit card transactions:  debit (PIN) and credit (signature).  When paying for a purchase, the clerk will ask "debit or credit" ? When you reply "debit" to the clerk, it becomes a PIN transaction.  You are required to enter your Personal Identification Number (PIN) after the card has been swiped through a point of sale terminal.  With PIN transactions, funds are withdrawn from your Checking Account immediately at the time of the transaction.  When you reply "credit" to the clerk, it becomes a signature transaction.  Signature transactions do not require your PIN but you do sign a slip to accept the transaction.  With signature transactions, funds are held in your Checking Account at the time of purchase until the transactions post to your account in one to three days.