This toolbar button 
 shows you the paid 
 invoices or cheques 
 for a selected customer or vendor in the Receive Payments or Pay My Bills 
 transaction windows. If this button is not 
 turned on, you can only see invoices and bills that have balances owing.
You can use this button to find a specific invoice or bill. This is very helpful if you need to void a payment after a cheque is returned by your bank (NSF cheque).