Banks see prepayment as suspicious/unusual activity and do not like it. They suspect kiting because the instrument used to prepay could in theory be reversed by the maker. This would leave them with exposure greater than your actual line of credit. Some cards allow you to go over limit like visa signature and some Amex and Diners Club m/c. My Diners told me 3.5 time the credit line is allowed. They said just dont make payment before it show online as posted. Payment before due date is always allowed.