You cannot cover a fee by adding the same percentage: the percentage is charged on the new, higher amount. That is why the formula divides by (1 − rate) instead of multiplying by (1 + rate). At 3%, the difference is small; at 10%, it is noticeable. The fee on a refunded payment is not added as a separate line because it is already included in the monthly fee. It is shown separately because you received nothing for that money—the product was returned, the payment went back, and the bank kept the fee.