When you place an order, we authorize two separate amounts. One amount, which is collected upon order placement, covers the Rental fee and, possibly, shipping. Similar to a ride-share or a taxi, the second amount reserves your funds. This way, if you'd like to keep any rented books, you can simply hold on to them – we'll deduct their purchase price and release the rest. If you decide to return all rented books, this pre-authorization will disappear, and no part of it will be collected.